Explanations for the 2018-2019 Official Step 2 CK Practice Questions

The NBME recently released an “updated May 2018” official “USMLE Step 2 CK Sample Test Questions,” but these are actually completely unchanged over the past two years since the June 2016 update, which was itself almost unchanged from the 2015 set.

Since it’s been a couple years, I’ve included the explanations below (which are, again, unchanged). You might see the comments on the old post for possible additional questions you may have. The multimedia question explanations are also at the bottom of this page.

Last year, helpful reader Jarrett made a list converting the question order from the online FRED version to the pdf numbers. I didn’t go through in detail to see if the online version order has changed, but the multimedia questions were in the same spots except that the block 3 question had shifted by one, so they may have done a little something.

Block 1

  1. E – Intermittent polyarthritis with positive ANA (sensitive but not specific) and anti-DNA (very specific) means lupus. You don’t even need the non-painful mouth ulcers.
  2. C – Anesthesia to the anterolateral thigh is the distribution of the lateral femoral cutaneous nerve. LFC neuropathy can be caused by compression near the inguinal ligament (say, from a hematoma). Note that it’s the compression of the nerve that causes decreased sensation, not the hematoma itself.
  3. H – Recurrent infections with abscesses should raise the suspicion of chronic granulomatous disease. Suppurative arthritis does even more, if you’re likely to remember that. The real diagnosis is made from the Step 1 style question. Nitroblue tetrazolium is the test used to diagnose CGD, which is a defect in NADPH oxidase (the oxidative burst that kills Staph aureus).
  4. D – Unstable and hypotensive patients after blunt trauma get laparotomies (don’t put an unstable patient in the CT scanner). In addition to saline and blood products, definitive surgery is how you address the C in ABC.
  5. B – Alcohol raises GGT. The other liver enzyme lab to remember is the 2:1 or greater AST/ALT ratio associated with alcoholic liver disease.
  6. D – The patient has a small bowel obstruction, likely due to adhesions from prior surgery, evident clinically and confirmed by radiograph (grossly dilated small bowel without distal colonic dilation to suggest paralytic ileus). Conservative treatment in a stable patient involves NG tube decompression and NPO. A CT can be obtained for further characterization and to look signs of bowel compromise (and would be in real life), but there is no reason to delay appropriate care to get it.
  7. A – Proximal muscle weakness + skin findings = dermatomyositis. Yes, kids can get this. In this case, they’ve gone to the trouble of describing Gottron’s papules (“flat-topped red papules over all knuckles”) and the heliotrope rash (purple-red discoloration over the eyelids). Please note the USMLE will never actually say things “heliotrope” on the actual exam. They always describe.
  8. A – Autonomy matters. If a patient has the capacity to make medical decisions (i.e. understands the risks) and is not an imminent harm to self or others (i.e. suicidal or homicidal), then he cannot be held against his will. We don’t institutionalize people just for noncompliance with medical treatment.
  9. A – This patient likely has classical Galactosemia, caused by a deficiency in galactose-1-P uridyl transferase deficiency, the enzyme that converts galactose and lactose to glucose. Intolerance to dairy, hepatomegaly/liver disease/jaundice with hypoglycemia due to decreased gluconeogenesis, and reducing substances in urine are classic. Listlessness and lethargy ensue with mental retardation and eventually death if untreated. Cataracts are also common. Hereditary Fructose Intolerance can present essentially identically. If you didn’t get to the underlying condition, the answer is still A. By process of elimination, given the serum hypoglycemia but no urine glucose, the issue is the inability to make glucose from stores (not to absorb it).
  10. C – Meningitis/encephalitis symptoms (fever, headache, altered mental status) with monocytic predominance and only mildly elevated protein on CSF studies go along with viral meningitis, such as HSV. Additional features (MRI findings of bitemporal signal changes and RBCs in the CSF from hemorrhagic necrosis) slam-dunk it but probably not necessary to memorize.
  11. D – Microcytic anemia is essentially always iron-deficiency unless there is a reason to suspect a thalassemia. In this case, extensive surgery has removed nutrient absorbing small bowel (the duodenum and proximal jejunum absorb iron).
  12. D – First-line treatment for panic disorder (and all anxiety disorders) is SSRI therapy. The only time you answer “benzodiazepine” (which wasn’t offered as a choice, because it would be arguable) for a panic disorder question is when they ask you what drug is “most likely to treat the episode” or something along those lines. BZDs work immediately; SSRIs take time.
  13. C – Polycystic ovarian syndrome (PCOS) is treated with estrogen-containing birth control (OCPs). Metformin would be an additional appropriate pharmacotherapy.
  14. D – Euvolemic hyponatremia means SIADH. Both brain and lung insults are common causes. Nonphysiologic secretion is “inappropriate,” of course.
  15. A – Repetitious vomiting leads to the classic hypokalemic hypochloremic metabolic alkalosis, as well as run of the mill dehydration (hyponatremic hypovolemia). So—low sodium, low potassium, low chloride, high bicarbonate.
  16. B – Endometriosis is a common cause of infertility and is associated with chronic pelvic/abdominal pain and excruciating periods. Gold standard for diagnosis is laparoscopy (visualization of “chocolate cysts”).
  17. D – Consider bacterial sinusitis to be analogous to bacterial pneumonia. All are possible, but Strep pneumo is the most common.
  18. B – Diabetes get diabetic nephropathy. Don’t over-think things.
  19. B – A cohort study (as opposed to a randomized controlled trial) is ripe for selection bias, which occurs when the treatment and control groups are not truly comparable. Matching for some factors (age, gender) doesn’t mean you’ve controlled for all possible confounders. That’s what randomization does!*
  20. D – Atopic dermatitis (eczema) is the “itch that rashes.” It’s one leg of the allergic triad: asthma, allergic rhinitis, and atopic dermatitis. Treatment is with topical steroids and rigorous emollient therapy.
  21. B – Repetitive vomiting (be it due to viral gastroenteritis or bulimia) leads to hypokalemic hypochloremic metabolic alkalosis. Alkalosis means elevated bicarbonate, which in this case is created as the byproduct of increased stomach acid production.
  22. D – Abscessed Bartholin’s cysts get incised and drained. When recurrent, they can be marsupialized, which isn’t as fun as it sounds.
  23. B – Catecholamines, such as those released by a functioning pheochromocytoma, are made by the chromaffin cells of the adrenal medulla. Episodic headache/hypertension is the tip-off here.
  24. A – Even if you forget the signs/symptoms of Kawasaki’s disease, which you shouldn’t (strawberry tongue is a giveaway), just remember it’s essentially the diagnosis for any child with 5 days or more of fever. Treatment is aspirin (the one time it’s okay in children, otherwise let’s avoid Reye’s syndrome) and IVIG.
  25. C – Macrocytic anemia with sensory changes is indicative of B12 deficiency. Causes include the classic pernicious anemia, but don’t forget the complications of GI surgery. Intrinsic factor is made by the stomach’s parietal cells.
  26. B – This patient has chronic (6 weeks) symptomatic hypotension while not coincidentally on three BP meds: a diuretic, a beta blocker, and an ACE inhibitor. The most likely explanation and easiest/fastest intervention is to reduce her polypharmacy.
  27. F – Premature babies get neonatal respiratory distress syndrome due to surfactant deficiency.
  28. B – Multiple lytic bone lesions equals multiple myeloma. Blastic/sclerotic lesions should make you think of metastatic prostate cancer (in men) and breast cancer (in women).
  29. B – Two things make this aortic dissection instead of a heart attack or pulmonary embolism. First, the diastolic murmur is that of aortic insufficiency/regurgitation, which is happening because the dissection is involving the aortic root. Second, the presence of diminished femoral pulses implies that the dissection also involves the descending thoracic aorta distal to the takeoff of the brachiocephalic and left subclavian arteries (which supply the arms). Only an issue in the aorta can cause that constellation of symptoms.
  30. F – TTP always seems like too many disparate symptoms but just remember the pentad: thrombocytopenia, microangiopathic hemolytic anemia, neurologic symptoms, renal failure, and fever. If the symptoms list seems super long, keep TTP in mind.
  31. A – An egg allergy is the most common contraindication to receiving the flu vaccine.
  32. G – Pleuritic chest pain and hypoxia with a normal chest x-ray should lead you to pulmonary embolism. There’s usually enough total lung and blood flow, but it’s the VQ mismatch that’s the issue.
  33. F – SIGECAPS+. Patient has MDD and developing panic disorder. Both of these can be treated first-line with SSRI therapy, such as paroxetine (Paxil).
  34. E – An acutely swollen painful great toe means gout (podagra). Gout is an inflammatory crystalline arthropathy. Aspiration reveals white cells and negatively-birefringent needle-shaped crystals. Pseudogout, which has rhomboid positively-birefringent crystals, more commonly affects the knee.
  35. F – Vasculitides like Wegener’s granulomatosis, microscopic polyangiitis, and others can cause poly-symptom disease and glomerulonephritis (hence the hematuria and proteinuria). Positive ANCA, (either P-ANCA or C-ANCA depending on the variant) is the key laboratory finding.
  36. E – LLQ pain with fever equals diverticulitis. The test of the choice is a CT scan of the abdomen with contrast.
  37. C – Bipolar disorder is the only reasonable answer, as evidenced by the increased energy, elevated mood, labile affect, and poor judgment and focus. You don’t develop ADHD at 32.
  38. A – Sudden respiratory failure after rupture of membranes means amniotic fluid embolism (it’s not like a fat embolism; it’s actually an allergic reaction). Can happen during labor or secondary to trauma. Hypotension and coagulopathy ensue.
  39. D – Fever, pain, and swelling behind the ear mean mastoiditis (remember the mastoid air cells?). The cause is nearly universally direct spread from otitis media.
  40. E – Exfoliative and blistering drug reactions come in three severities of the same mechanism: erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis. Diffuse involvement (>30%) is consistent with toxic epidermal necrolysis (TEN), which carries a 30-40% mortality.

Block 2

  1. E – Pseudogout (calcium pyrophosphate deposition disease) is an inflammatory arthritis with a predilection for the knee that causes synovial calcifications.
  2. A – Low pH means acidemia. Renal failure causes metabolic acidosis (hence low bicarb). Low CO2 is the respiratory compensation. If it was vice versa, the pH would be high (alkalemia).
  3. A – Lisinopril and especially spironolactone (a K-sparing diuretic) can both cause hyperkalemia. Renal failure (severe AKI or ESRD) is also a major cause of hyperkalemia, but not in this case with the only mildly elevated Cr and BUN levels.
  4. A – The differential for chronic diarrhea in an AIDS patient includes bacterial, viral, and parasitic causes as well as HIV enteropathy. Cryptosporidium is a protozoa that classically causes watery diarrhea in AIDS patients, especially those exposed to unclean water sources (hence the traveling to Asia). CMV is a reactivation infection and MAC is ubiquitous; disease caused by either of these pathogens is due to severely depressed immunity (i.e. CD4 < 50).
  5. A – Headache and stiff neck clue you to meningitis. In a college student, that’s enough for the diagnosis of meningococcal meningitis. Stop reading. The treatment is ceftriaxone.
  6. F – Weight loss and worsening lung symptoms in a smoker mean lung cancer. Non-small cell is by far the most common variety. The small cell variety on tests will usually have fun paraneoplastic syndromes.
  7. B – Wide split fixed S2 is an ASD.
  8. C – Weight loss and iron deficiency anemia are concerning for colon cancer with occult blood loss. Colonoscopy is required. Parasitic causes of iron deficiency (e.g. hookworm) are first tested with stool ova & parasite screening.
  9. A – Dermatomal rash means zoster (a chickenpox/varicella reactivation disease). Immune insults, like chemotherapy, predispose to zoster flares.
  10. D – Transillumination of a scrotal mass equals a hydrocele, which is due to a patent processus vaginalis.
  11. E – Working up serious hypoglycemia involves measurement of both insulin and C-peptide (the cleaved by-product of endogenous proinsulin) to assess for hyperinsulinemia and distinguish endogenous (e.g. insulinoma) from exogenous (e.g. Munchausen’s) causes. “Nurse” is a common Munchausen tip-off (someone with the know-how and skills to pull it off well).
  12. C – Interstitial nephropathy (also known as tubulointerstitial nephritis) is most commonly an allergic-type reaction to medications, typified by eosinophils in the urine. The nonspecific maculopapular reaction is also the common type of drug reaction rash and is seen in a minority of cases, as is low-grade fever (not critical to the question). Several medications can cause this: penicillins, cephalosporins, and NSAIDs are the most common.
  13. D – Pinpoint pupils are a classic tip off for opioid use (caused by parasympathetic activation). Additionally, neither alcohol nor barbiturates would be likely choices in this context because they have similar effects (along with benzodiazepines).
  14. C – Patients who have the capacity to make medical decisions are allowed to refuse life-saving medical treatment. You should offer it but accept her refusal.
  15. B – A p-value less than 0.05 means that the results are statistically significant. However, most would agree that roughly 7 hours difference in cold duration is clinically insignificant.
  16. E – ABCs. Patient has an airway (evidenced by breath sounds without mention of other complicating factors like unconsciousness). Move on to breathing. Asymmetry implies a hemo-, pneumo-, or hemopneumothorax, which requires a chest tube immediately.
  17. E – Crescents mean rapidly progressive glomerulonephritis (RPGN—bad news bears). Immune complexes along the basement membrane mean Type II, such as seen with lupus, IgA nephropathy, acute proliferative glomerulonephritis, and Henoch-Schönlein purpura. Treated with immune suppression, which in the acute phase always means steroids.
  18. A – Cough is often the only sign of asthma. Exercise-induced asthma is exercise-induced asthma.
  19. E – Bronze diabetes and arthritis means hemochromatosis. They never say the words “bronze diabetes” on board questions, but it doesn’t mean it’s not there. You don’t want an awesome tan on the boards.
  20. A – Repeated microtrauma from repetitive stress can cause thrombosis. DVT leads to erythema and venous engorgement, the other choices do not. For bonus points, the eponym for effort-induced upper extremity DVT is “Paget–Schroetter disease” (for those keeping track at home).
  21. D – The radiograph is showing complete collapse of the left lung (2/2 mucous plugging) with resultant severe ipsilateral mediastinal shift. An acute shift can have the same effect as any other “tension”-type process, causing impaired venous return to the heart and decreased cardiac output via the Starling mechanism.
  22. E – Weight gain, fatigue, and constipation go with hypothyroidism. High LDL cholesterol actually does too, but the question is doable even when ignoring the lab values.
  23. A – Organ donation is a complex organizational dance, and the regional procurement organization manages the nitty-gritty aspects.
  24. A – They’ve listed the criteria for ADHD. Note that conduct disorder is the kid-version of antisocial behavior. If the kid breaks rules and messes up but doesn’t seem evilthen it’s not conduct disorder.
  25. D – Abdominal pain is a common presenting complaint of DKA, which is a common presentation of new-onset type 1 diabetes. Note the glucose of 360.
  26. E – Abnormal vaginal bleeding in a woman over 35 requires an endometrial biopsy to rule out endometrial cancer.
  27. A – It’s not clear that the glucose is a fasting value or not, but it’s clear that the patient has symptoms of diabetes in the context insulin resistance (obese kid with acanthosis nigricans). Diet and exercise are always necessary in DM2 and can reverse many early cases. With a 10% weight loss, for example, the patient may not require pharmacotherapy.
  28. B – Marfan syndrome (you know, hinted at by the familial tall stature and weak hypermobile joints) is associated with a dilated/aneurysmal aortic root, which can worsen, dissect and/or rupture if not monitored.
  29. D – Meniere disease is characterized by recurrent vertigo attacks associated with ear fullness, tinnitus, and hearing loss.
  30. C – Follow your ABCs. Tachycardia and hypotension mean severe volume loss necessitating aggressive intravenous fluid resuscitation.
  31. A – Totally healthy people with indirect hyperbilirubinemia means Gilbert syndrome (which causes decreased bilirubin conjugation due to reduced glucuronyltransferase activity).
  32. D – Mitral valve stenosis is a sequela of rheumatic heart disease that can lead to LAE and left-sided heart failure if left untreated.
  33. B – Folic acid prevents neural tube defects. End stop.
  34. A – The primary mechanism by which beta-blockers reduce angina is via decreased contractility, which reduces the oxygen demand of the myocardium (which has a constrained supply due to coronary artery disease). Lowering heart rate also helps, but that isn’t one of your choices.
  35. B – One of the in SIGECAPS is for suicidality. Depression is extremely common, and it’s also underdiagnosed and undertreated in cancer patients.
  36. C – Again, acute RUQ pain (especially in an obese woman) should set off the gallstone alarms. Fever and other systemic signs, white count, etc lead you down the acute cholecystitis. Simple pain leads you to symptomatic cholelithiasis. Either way the first step is to get a RUQ sono to see those stones! HIDA is used as an adjunctive study in cases of cholelithiasis to assess for cystic duct obstruction (and thus likely acute cholecystitis) in equivocal cases.
  37. D – Walking pneumonia is treated with macrolide antibiotics as first line. Patchy infiltrates in a patient with clinical pneumonia symptoms who otherwise young, healthy, and walking around…think mycoplasma.
  38. B – They describe claudication and vascular insufficiency with strong flow in the groin and no palpable flow distally in the dorsalis pedis, placing the level of stenosis somewhere in between (i.e. femoropopliteal). Diabetes and smoking are two big risk factors for peripheral arterial disease (PAD).
  39. C – We can only put the laboratory tests into context if we have an accurate gestational age. Since her LMP is unreliable (totally unknown), we need an ultrasound to date her pregnancy. The most common cause of an abnormal MSAFP is wrong dates.
  40. B – Post-traumatic AV fistula! Just like dialysis AV fistulae have bruits and thrills, so do non-purposefully created ones. These can take a long time to form but can be associated with steal syndromes due to decreased perfusion to the distal extremity, venous incompetence, varicosities, and eventually stenoses due to unreasonably high flow, and even high-output heart failure.

Block 3

  1. A – This patient has urge incontinence, which is commonly caused by detrusor instability (and can be treated with anticholinergics like oxybutynin). This is opposed to stress incontinence, the other most common type, which is worsened by abdominal pressure/coughing/laughing/etc and can be caused by pelvic floor prolapse secondary to multiple childbirths etc. Neurogenic bladder can cause overflow incontinence.
  2. B – Lumbar strain doesn’t require specific treatment or workup. Bed rest (old school idea) has actually been shown to worsen outcomes.
  3. A – Most common palpable breast mass in women less than 30 is fibroadenoma. In women between 30-50, it’s a cyst (or fibrocystic changes of the breast). Greater than 50, malignancy.
  4. E – The thing you do with things that look like skin cancer is excise them completely.
  5. D – A boot-shaped heart means Tetrology of Fallow on board exams. Outside of that rare straight-up buzzword giveaway, TOF is by far the most common cause of cyanotic heart disease.
  6. A – Via urinalysis and renal ultrasound, we’ve excluded serious/treatable causes of renal hypertension including Conn’s disease (hyperaldosteronism) and renal artery stenosis such as due to fibromuscular dysplasia. That leaves her obesity.
  7. B – Asymptomatic bacteriuria is never treated, except in pregnancy, when it should always be treated due to its association with preterm labor. Treat with an oral antibiotic that covers gram negatives (like E coli), such as amoxicillin or nitrofurantoin.
  8. D – You know what causes sudden onset headache and neck stiffness? Subarachnoid hemorrhage. The first episode can be transient, the so-called sentinel bleed before a catastrophic aneurysmal bleed.
  9. D – The description of a primary lung cancer with associated muscle weakness is leading you to Lambert-Eaton myasthenic syndrome, a paraneoplastic autoimmune condition where antibodies attack the presynaptic calcium channels of the neuromuscular junction. Lung-cancer paraneoplasias are test favorites.
  10. A – Frequent turning prevents the development of pressure ulcers in patients with decreased mobility.
  11. A – PTSD symptoms that begin within 4 weeks of a traumatic event and last 4 weeks or less is acute stress disorder (ASD).
  12. B – The drugs of choice for Alzheimer’s-type dementia (i.e. general dementia without specific factors to make you consider other diagnoses) are the cholinesterase inhibitors, the most important of which is Donepezil.
  13. D – Painless uterine bleeding goes with placenta previa. Painful uterine bleeding goes with placental abruption. Ruptured vasa previa results in rapid loss of the fetus.
  14. F – Septic arthritis (rapidly warm swollen joint +/- fever) must be tapped, followed by antibiotics. Untreated, the joint can be destroyed in days. Minor trauma can predispose to hematogenous bacterial spread.
  15. B – The first imaging test in acute stroke is a noncontrast CT scan of the head. At 12 hours out, it may show ischemic strokes, but more importantly, it will diagnose hemorrhagic strokes, for which reperfusion and antiplatelet therapies are contraindicated.
  16. B – Myocardial infarction causes heart muscle death (as the name implies). Lose enough muscle and you get systolic heart failure.
  17. B – Thick, white, and acidic means candidal vulvovaginitis (aka a yeast infection). Bacterial vaginosis typically only causes foul/fishy odor (and is alkaline, has a positive whiff test, clue cells on wet mount, etc).
  18. E – Thrombocytopenia without antiplatelet antibodies or splenomegaly implies a platelet production problem (e.g. myelofibrosis). History of radiation therapy is a risk factor. The only way to know what’s happening at the factory is a bone marrow biopsy.
  19. C – Multinodular goiter! Say it five times fast. Feels good, doesn’t it? The first half describes blatant hyperthyroidism. The thyroid scan is now demonstrating an enlarged gland with multiple nodules (“areas”), some avid/hyperfunctioning and other relatively depressed (either not “hyper”-functioning and thus relatively cold or actually cold, most commonly filled with colloid).
  20. C – Obstructive sleep apnea (OSA) is diagnosed exclusively by polysomnography (aka a sleep study).
  21. E – Everyone should get a flu shot. Diabetics are relatively immune suppressed and deserve it even more.
  22. D – A nagging persistent dry cough is a common side effect of ACE-inhibitors due to bradykinin accumulation (bradykinin is normally degraded by ACE). Along with angioedema, it’s an important reason for discontinuation; the solution for both is to switch to an angiotensin II-receptor blocker (ARB) like losartan, which does not affect ACE activity directly.
  23. A – RUQ pain and nausea after meals is concerning for symptomatic cholelithiasis. The test of choice is RUQ sono to assess for stones.
  24. A – It’s a cholesteatoma, which can be congenital (rare) or acquired (much more common). Even if you have no idea what that is (look it up), it’s the only answer with “proliferation” to go along with the mass. None of the others mention anything remotely mass-like.
  25. A – The most common cause of hypothyroidism in developed countries is Hashimoto’s thyroiditis. In developing countries, it’s iodine deficiency.
  26. D – If environmental, food, or exposure allergies ever include shortness of breath, hoarseness, or anything remotely airway-involving or anaphylaxis-like, then carry an epi-pen.
  27. D – STDs are always double-treated for both chlamydia and gonorrhea, as coinfection is extremely common, and clearance is crucial to prevent reinfection and continued spread. That means anyone with cervicitis or urethritis gets azithromycin or doxycycline with ceftriaxone.
  28. D – The majority of twins are born premature, which is even more true for triplets. Only monochorionic twins experience twin-twin transfusion syndrome (as they have to share a blood supply in order for the problem to occur).
  29. B – Confusion and tremulousness a few days after an unexpected hospital admission on the USMLE means alcohol withdrawal (unanticipated detox).
  30. B – The STD that forms a painful ulcer aka chancroid = H ducreyi (ducreyi makes you cry, as they say).
  31. D – The lungs are clear. Location, JVD, and lack of heart sounds mean cardiac tamponade from hemorrhage into the pericardium. Pericardiocentesis is the next step. Don’t forget, if you see tension pneumothorax or a water-bottle heart (from tamponade) on chest xray, you’ve already delayed life-saving therapy.
  32. D – The inclusion bodies signify that this patient has a CMV infection of the renal transplant, which can originate from either the donor or recipient but are activated/unmasked by immune suppression. CMV is an important cause of morbidity and mortality in renal transplants and both the donor/recipient are routinely screened.
  33. E – Don’t let the carpal tunnel history fool you. Numbness of the pinkie and half of the ring finger is ulnar entrapment (cubital tunnel syndrome, which happens at the elbow); carpal tunnel syndrome is the median nerve at the wrist (affecting thumb, index, middle, and half of the ring)
  34. E – Genital warts don’t hurt and they turn white with vinegar (acetic acid). No systemic therapy works (although there is now a vaccine), but cryotherapy (as well as laser and electrocautery) can help. HPV will remain, however, and the lesions can recur.
  35. C – Remember cystic fibrosis in young people with worsening obstructive lung disease and frequent infections. The infertility in males is secondary to failure of the vas deferens to develop properly (in women, it’s due to thick cervical mucus). Sweat chloride test makes the diagnosis.
  36. D – Fever, AMS, and muscle rigidity in a patient on antipsychotics (aka ‘neuroleptics’) means neuroleptic malignant syndrome (NMS). Very rare, very dangerous.
  37. B – IBS is a “functional” G.I. problem, which means that it is a diagnosis of exclusion (must rule out IBD, Celiac, etc). You may have enjoyed its recent popular appearance on television as a disturbing anthropomorphized walking bowel. Common symptoms include diarrhea, constipation, pain relieved by defecation, and flatulence, often subject to a degree of emotional valence. As such, like headaches, IBS symptoms can be improved by TCA therapy, such as nortriptyline.
  38. D – They hit you over the head with hypocalcemia symptoms before giving the value. Hidden in there is the pancreatic insufficiency causing steatorrhea and fat-soluble vitamin deficiency (A, D, E, and K).
  39. B – The patient has rhabdomyolysis from a prolonged visit with the floor. The ridiculously high CK confirms the diagnosis. Rhabo causes renal failure and requires aggressive fluid resuscitation.
  40. B – Type II error is the possibility of producing a false negative (a negative result when it should be positive). A smaller sample size may not be able to detect a small (but real) treatment effect and thus increases the chance of type II error.


Multimedia questions:

Block 1

7. A – Classic Moro reflex, entirely expected and normal until it disappears around age 4 months. If you have never seen a newborn before, also note that the mom is concerned about delayed milestones at two weeks of age, which is a red flag for BS: babies aren’t even smiling socially yet by two weeks.

Block 2

3. D – Pill-rolling resting tremor of Parkinson’s disease secondary to loss of dopamine neurons in the substantia nigra.

18. A – I’m going to point out that a normal healthy kid with no cardiac history or symptoms and no family history of sudden cardiac death for a pre-sports physical is probably going to have a benign exam no matter what you think you hear. HOCM is what you want to exclude theoretically, but here we don’t have a real systolic murmur, just a little vibratory flow murmur at LLSB.

33. E – This one is a bit silly. The lung exam is normal outside of the super common basilar crackles. Everything except for PE you would expect to hear a more impressive auscultation abnormality. But for this question: B and C take longer than 3 days. D we would expect fever, productive cough etc. Bronchitis would be possible, but still more often to have at least productive cough if not fever. PE, on the other hand, classically has a nonproductive cough, hypoxemia, and tachycardia. All three are present. And then they mention her med: OCPs, which are an important predisposing factor for PE in young women for whom it is otherwise a rare entity. Young lady on OCPs is a classic set-up for an STD question (who needs condoms?) or a PE question, one of the two.

Block 3

10 D – Statistical significance (a low p-value) does not equal clinical significance. A favorite teaching point when it comes to interpreting literature.

11 C –A & D are conjectures: the kind of statements people drop inappropriately in the conclusion of a weak paper to make it sound important. E is an exclusion criterion. B is the opposite: including 0 is equivalent to something not being significantly different.


Corrections, clarifications, copy/paste errors etc can be made/asked/mocked in the comments below.


Constantine 06.23.18 Reply

Hello. Thank you for your explanations.
Just one correction – they changed sequence of answers in question #74, the same explanation but answer is “A” in new pdf.

Ben 06.23.18 Reply

Thanks for the heads up! They do things like that every so often, can’t imagine why. Fixed now.

Bonnie 07.10.18 Reply

This is great. I wish the educational objectives on uworld were written by you. Or… you should make your own qbank! There comes a point in studying where you no longer need the long educational explanations but rather need to start honing your question-reading/interpreting skills, which you have a knack for. This is the closest resource to that I’ve seen. I think I read one of your articles last year on how to read questions and my scores really jumped. So again, thanks!

Ben 07.17.18 Reply

Very welcome!

I had illusions of doing something like that many years ago (actually it was really writing a Step 2 CK text with these sorts of things in mind), but alas I didn’t do it!

Ephraim Mandell 07.16.18 Reply

I hope you go into medical education besides standard clinical radiology. The standard answers applicants offer in medical school interviews consist of the platitudinous ” I want to help people, I enjoy helping people….etc.” You have, by aiding and enriching the educational process of medical students, are in fact helping hone the skills of the very doctors who in short order will be providing help, and relieving suffering. I think of your contributions as a pebble thrown into a lake, and the wave of influence radiates in concentric circles outward.

Ben 07.17.18 Reply

Thank you for those very kind words. I am happy to report that—in addition to this site—I will indeed be working with radiology residents and medical students in my new position.

AA 07.24.18 Reply

Thank you so much for all of these explanations! Just one question – number 57 aren’t immune complex deposition hypersensitivities Type III?

Ben 07.24.18 Reply

Type II RPGN, not Type II hypersensitivity. Type I being anti-BM antibodies as in Goodpasture’s and Type III being the pauci-immune variant.

Ruben 08.11.18 Reply

hey just want to thank you for your content, has helped me with step 1, and step 2, hoping step3 content comes in soon because some of these questions are funky !! .. once again i can speak on everyones behalf when i say thank you

Kelly 10.10.18 Reply

hello, how much would you say free 120 correlates to step 2 ck?

Ben 10.10.18 Reply

Same types of questions, so perfectly. If you mean score-wise, impossible to say. They might be the same as the Step 1 correlations (https://www.benwhite.com/medicine/step-1-correlations/), but they might not.

Jake Gold 10.18.18 Reply

Just wanted to point out #10 is actually likely HSV encephalitis given the hyperintensities in the temporal lobes (which HSV has tropism for) and the elevated erythrocytes are key in this because they indicate hemorrhagic necrosis of the temporal lobes (classic in HSV encephalitis).

Ben 10.18.18 Reply

I completely agree, however, the additional features more specific to HSV are not necessary to answer this particular question correctly.

Akanksha 11.15.18 Reply

Hi, Thanks for the explanations.
I had a doubt though, in 80th question how do we rule out/differentiate pseudoaneurysm?

Ben 11.15.18 Reply

Pseudoaneurysms don’t cause venous shunting.

George 03.27.19 Reply

84 is likely squamous cell carcinoma

SZ 05.30.19 Reply

Hi there. Thank you for your explanations! For number 4, I don’t understand why a thoracotomy wouldnt be done. From the question stem, I understood this to be an esophageal rupture… Thank you for the clarification.

Ben 05.30.19 Reply

Actually I think they were getting at a traumatic diaphragmatic hernia.

K.O. Doc 07.05.20 Reply

“Upper thoracic esophageal perforations are approached by a right thoracotomy and left thoracotomy for the lower third. Lesions at the esophagogastric junction are approached by left thoracotomy or upper midline laparotomy” I found this on a pubmed article. I guess that the reason there was so much green fluid was because the rupture was in the gastro-esophageal junction and thus stomach contents were leaking into the thorax. In which case its preferred to do a laparotomy.

Karishma 07.02.19 Reply


thanks so much for these explanations. There are a few things I still don’t understand though, maybe you could help clarify.

115. If he has CF, why would he just have symptoms for the past 4 years? Also isn’t it associated with absence of vas deferens, so wouldn’t he have no sperm count instead of a low sperm count?

118. I understand why he would have vitamin D deficiency, but in that case, his PTH would increase and take calcium from his bones and kidneys before he got so hypocalcemic, so wouldn’t the ultimate issue be hypoparathyroidism?

119. She already has ATN as evidenced by the pigmented granular casts in her urine sediment. So in the next 24 hours wouldn’t she be at risk for cerebral edema do to accumulation of nitrogenous substances?

120. I just don’t get this at all. Isn’t a small sample size equally likely to find a difference that isn’t really there? (Type 1 error)

Thanks so much!

Ben 07.05.19 Reply

115 > Think you’re reading too much into it. CF is a heterogenous disease, not everyone will be devastated as a child. Around 98% of patients have absence, but not all.

118 > No, the root cause here is Vit D deficiency. You just described secondary hyperparathyroidism, not hypo, which was the answer choice.

119 > The pigmented granular casts are related to myoglobinuria, which is a risk factor for ATN, which has tubular epithelial casts. I think you’re overreading these.

120 > Power and type II error are inversely correlated. See https://en.wikipedia.org/wiki/Power_(statistics).

Jonathan Stroup 07.13.19 Reply

Not sure where I’m off on question 42, but I used Winter’s formula which gave me a corrected CO2 of 30.5 +/- 2 seems like that makes it uncompensated (albeit only just)?

Ben 07.13.19 Reply

Winter’s formula gives the expected range of respiratory compensation in a pure metabolic acidosis.

14*1.5+8 = 29 +/- 2 gives a range for expected respiratory compensation range of 27-31. The value they provided of 28 falls right in that range. So looks like your math was off.

Do 07.18.19 Reply

Hi there!
Thanks for your great job!
I have 2 questions :)
In block 1, question 4 what was the diagnosis? I was thinking about esophageal rupture.
What percentage do you think is good enough for taking the exam? I had 76 % after taking the entire exam. Do you think is good enough?

Ben 07.18.19 Reply

Probably a traumatic diaphragmatic hernia. Esophageal perforation results in pneumomediastinum as the predominant radiographic feature.

There’s no good number I know of for this set. Certainly that’d be passing. If the correlations are similar to the Step 1 set, it’d be something like these: https://www.benwhite.com/medicine/step-1-correlations/

K.O doc 07.05.20

So the patient had a traumatic diaphragmatic herniation of the stomach into the thorax and they perforated the stomach with the chest tube and that’s why it drained air + green fluid? Thats the only thing that makes “logical” sense.

Droov 07.23.19 Reply

#99 is actually hypothyroidism because of Hashimoto’s disease. Fatigue, dry skin, brittle hair, and cold intolerance are classic HYPO-thyroid symptoms. (Straight hair is hyper-thyroid). Thyroid is bigger because of compensatory TSH stimulation that causes thyroid hypertrophy.

Droov 07.23.19 Reply

nvm! wrong block haha

Ben 07.23.19

yep, that’s #105.

Munib Francis 07.28.19 Reply

Love the explanations Ben, Thanks so much! I was mulling over a couple and came to some nice conclusions.

#118. Given that the patient has a a history of chronic alcohol abuse and several episodes of acute pancreatitis, combined with his 30 lb weight loss and physical exam findings of cachexia and ill appearance, I would assume he has pancreatic cancer causing the pancreatic insufficiency.

#117. I’ve read in several prep sources that SSRI/SNRI’s can also be used in IBS, especially in those with constipation-predominant IBS or concomitant depression. However, according to uptodate evidence is not adequate for SSRI’s. Meanwhile evidence is sufficient for TCA’s, especially in diarrhea-predominant IBS, likely you due to the additive affect of the anticholinergic properties.

Ben 07.28.19 Reply

I wouldn’t assume cancer, though certainly possible; the question certainly doesn’t ask you to. Chronic alcoholism and exocrine insufficiency alone can account.

Lissette 08.07.19 Reply

Hello there!
Thank you very much for the explanations! and even more for the way of doing it! I’m truly amazed of your work. Thank you, again.
I have a question;
Is there any effective technique I could use when I’m facing an abstract questions? I normally just leave them for last, because I panic every time I see that amount of info all together, and then I just look back and forth through the entire thing over and over until I run out of time… horrible, I know…. I will appreciate any tip you could give me, thank you!

Ben 08.09.19 Reply

One key is to be very comfortable with the basic stats that these questions often hinge on. If you’re able to rapidly extract which parts of the content reflect which parts of the formulas you’re used to, you can usually get through the question a lot faster.

Mirna 08.16.19 Reply

Hi! Thank you for doing this! It is very helpful.
Block 1, question 17: I had a UWorld question that stated that nontypeable Hib is the most common cause of acute bacterial rhinosinusitis (~40-50%) then moraxella and then strep pneumo (in decreasing order).

Ben 08.18.19 Reply

That may be true but is not the classic teaching. As a practical matter, the real most common organisms for anything do tend to have some regional variation. The NBME has continued to use this classic question but I wouldn’t consider myself wise enough to say if they’re out of date compared to the UW or if that is likely to change on current exams.

Mirna 08.16.19 Reply

Block 1, #26: Do you know what the significance is of the changes between the L & R arm? That tripped me up! Thank you!

Ben 08.18.19 Reply

Subclavian occlusion vs critical stenosis, which is the cause of the vertebral artery reversal (subclavian steal). It’s essentially a distractor.

sanjana 08.25.19

q 61. First, thanks Doc for to-the-point , logical explanations!
I have a doubt, How will we differentiate between pneumothorax and atelectasis? because the Xray made it look like R pneumothorax to me! And it looked like atelectasis on the L side, true, but would really appreciate if you could give me a common sense way to d/b the two!

Ben 12.24.19

You need to see a pleural line for a pneumothorax where there is pure air without lung marking accumulating outside of the lung proper. Not just a dark looking lung.

The image quality here is really sufficient to show that anyway. But regardless a R PTX wouldn’t explain the left appearance, and USMLE is a world with a single best answer.

The real differential for a white-out lung field on CXR is a collapse versus a large pleural effusion. The differentiation is the volume. Atelectasis will shift the mediastinum toward the collapsed lung due to volume loss. Pleural effusion will be either neutral or have contralateral mass effect/shift.

Molly 12.23.20

Why not give her warfarin though to resolve the subclavian steal? Isn’t that caused by an occlusion in the subclavian?

Ben 12.24.20

Warfarin doesn’t reverse arterial stenosis; it’s used to treat (and prevent recurrences) of venous thrombosis. But even if it did, that answer is still wrong. The primary issue here is global hypotension here due to mis-titrated antihypertensive medical therapy.

sanjana 08.25.19 Reply

q 95. shouldnt there be pancytopenia is the BM is blasted?

Jon D 07.07.20 Reply

#68, isn’t the stem describing ehlers-danlos syndrome? not be nit-picky, just wondering. I know they are both CTDs and the answer choice would be the same.

Ben 07.07.20 Reply

Perhaps, there’s overlap. Vision (ectopia lentis) and cardiac (mitral valve prolapse) problems more common in MFS and are both suggested in the stem. Also the absurd tallness. But EDS is a heterogeneous group of disorders. Both have joint hypermobility but I agree they do focus on that feature (though also without the skin findings and easy bruising that often accompanies it in EDS).

Bindi 07.21.20 Reply

I believe 9 (block 1) is actually Hereditary Fructose Intolerance. The negative urine glucose but positive reducing substances point to that. It doesn’t make sense for classic galactosemia, since they start showing symptoms pretty much right when they start drinking milk and present in the first few days of life. The patient in this stem was 2 months old, and symptoms only started 6 weeks prior to that.

Ben 07.21.20 Reply

Possibly, though I’m not sure there’s enough in the stem to be definitive, and there’s a ton of clinical and lab overlap. The correct answer doesn’t change here regardless, and that’s probably on purpose.

sp 08.17.20 Reply

#11 – why not anemia of chronic disease? no ferritin so I can’t see how you can really differentiate..

Ben 08.17.20 Reply

You have to pick the BEST answer; not pick all plausible answers.

While anemia of chronic disease can be normocytic or microcystic, it’s frequently normocytic, especially on tests. The most common cause of microcytic anemia by far is iron-deficiency. They’ve given you a cause for iron-deficiency in the surgical history in addition to the fact the patient is presumably a menstruating female; meanwhile, they mention no evidence of active Crohn’s nor is she on any medical therapy for it.

Seyma Bilgin 02.05.21 Reply

Block 1 Q.28 Multiple Myeloma
Why this pt leukocyte count is high? May be due to pt has pnemonia at the same time but i though leukocyte is low in MM.

Ben 02.05.21 Reply

Yes, the patient has PNA, which exams the leukocytosis. Regardless, the white count here is really not germane to the answer of the question given the imaging findings. The teaching point is multiple lytic lesions = mets or myeloma.

su 02.06.21 Reply

#118 Why this pt dtr +4 with hypocalcemia?

Ben 02.06.21 Reply

It may be counterintuitive, but remember that it’s hypocalcemia that results in neuromuscular irritability with tetany, spasms, Chvostek’s and Trousseau’s signs, and hyperactive DTRs.

Abel 05.03.24

Calcium normally has inhibitory activity on Na channels decreasing excitability of muscle fibers. When calcium is low hyperactivity is seen.

Natasha 08.15.21 Reply

For question 43, why wouldn’t metabolic acidosis be the cause of the hyperkalemia. I was thrown off by the HCO2 at 18 (normal is 22-28) and know that acidosis goes along with hyperkalemia

Natasha 08.15.21 Reply

Additionally, for question 81 why can’t the answer be UTI. I thought UTIs can also cause urge incontinence and she does have occasional bacteria in urine and an atrophic cervix (could be genitourinary complications of menopause)

Ben 08.15.21

A 20-year UTI?

As a general rule, the thrust of answering the question is never “Why can’t it be X?” – it often can be. The question is, of the provided choices, which is the best answer.

Ben 08.15.21 Reply

We would be very unlikely to see severe hyperkalemia of this degree caused merely by this degree of mild renal failure and mild acidosis.

Richard 05.13.24 Reply

Thanks for this Ben. F/u on q61:

My understanding was that there’s an atelectasis causing the ipsilateral mediastinal shift and the root cause of all the problems here. It seems a better explanation for the hypotension than just “reduced CO”. Not sure what I’m misunderstanding and how to approach similar situations in the future – any suggestions?

Additionally, about starting a thiazide in the child who has had sustained BP in 150-160s in q86

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