Explanations for the 2014-2015 Official Step 2 CK Practice Questions

Update 8/5/2015:  They’ve now updated to the new 2015-16 question set and removed the old links (they’ve previously kept the old ones working for several years). You can still access cached versions of 2014-15 and 2013-14 for now (cachedview.com is helpful in cases like these). My explanations for the new set are available here.

Here are the explanations for the updated 2014 (effectively 2014-15) official “USMLE Step 2 CK Sample Test Questions,” which can be found here.

Overall, there are only three new questions when compared with last year’s set (#90, 95, and 104), which I’ve marked with asterisks below. The explanations for the earlier 2014 set (effectively 2013-14) set can still be found here (the question pdf is still available online) and are largely identical (though in completely different order).

Block 1

1. F – TTP always seems like too many disparate symptoms but just remember the pentad: thrombocytopenia, microangiopathic hemolytic anemia, neurologic symptoms, renal failure, and fever.
2. D – Fever and lower abdominal pain during pregnancy equals endometritis. Infection is a major cause of PROM.
3. C – Notice the pale, hypoperfused eyeball here. The sudden onset should have ruled out A, B, and E for you. Central retinal vein occlusion blocks the outflow of blood from the eye, leaving a bloody engorged mess. It also typically presents more gradually. Central artery occlusion is one cause of amaurosis fugax.
4. A – Totally healthy people with indirect hyperbilirubinemia means Gilbert syndrome (which causes decreased bilirubin conjugation due to reduced glucuronyltransferase activity).
5. A – A friction rub and diffuse low-grade ST-segment elevation equals pericarditis.
6. 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 mismatch that’s the issue.
7. F – Premature babies get neonatal respiratory distress syndrome due to surfactant deficiency.
8. D – Bartholin’s cysts get incised and drained. When recurrent, they can be marsupialized, which isn’t as fun as it sounds.
9. A – It’s a cholesteatoma, which can be congenital or acquired. 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.
10. D – A boot-shaped heart means Tetrology of Fallot on board exams. Outside of that giveaway, TOF is by far the most common cause of cyanotic heart disease.
11. B – Endometriosis is a common cause of infertility and is associated with chronic pelvic/abdominal pain and excruciating periods. Formal diagnosis is made using laparoscopy (visualization of “chocolate cysts”).
12. A – Frequent turning prevents the development of pressure ulcers in patients with decreased mobility.
13. B – Altered consciousness (intoxication, seizure, etc) predisposes to aspiration. Aspiration PNA typically goes to the RLL when upright and RUL when supine, and the damage is done by nasty GI anaerobes.
14. 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.
15. 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).
16. C – Polycystic ovarian syndrome (PCOS) is treated with estrogen-containing birth control (OCPs). Metformin would be an additional appropriate pharmacotherapy.
17. F – SIGECAPS+. Patient has MDD and developing panic disorder. Both of these can be treated first-line with SSRI therapy, such as paroxetine (Paxil).
18. 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.
19. B – Confusion and tremulousness a few days after an unexpected hospital admission on the USMLE means alcohol withdrawal (unanticipated detox).
20. 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.
21. A – Nighttime cough and hoarseness imply laryngopharyngeal reflux (GERD that spills over into the larynx). In real life, you might try a PPI trial, but pH monitoring will confirm the diagnosis.
22. E – Everyone should get a flu vaccine. Diabetics are relatively immune suppressed and deserve it even more.
23. B – You can usually ignore the CT scan if you want. Elevated lipase, epigastric pain radiating to the back, and alcoholism go best with pancreatitis. Varices present with hematemesis. Perforated gastric ulcers will give you free air (also typically blood in the stool as well).
24. B – One of the S in SIGECAPS is for suicidality. Depression is extremely common, and it’s also underdiagnosed in cancer patients.
25. A – Headache and stiff neck clues you to meningitis. In a college student, that’s enough for the diagnosis. Stop reading. The treatment is ceftriaxone.
26. C – If you see blood at the meatus, don’t just jam a foley into it. You can transect a damaged urethra. Get a “RUG” (retrograde urethrogram).
27. 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.
28. E – ABCs. Patient has an airway (evidenced by breath sounds). Asymmetry implies a hemo-, pneumo-, or hemopneumothorax, which requires a chest tube immediately.
29. B – This man is well-controlled. Nonetheless, diabetics need monitoring for end-organ damage, specifically of the eyes, kidneys, and peripheral arteries. Diabetics should undergo annual ophthalmologic examination.
30. C – Nifedipine (a peripherally-acting CCB) can be used to treat Raynaud’s phenomenon, which is a painful vasospastic condition associated with scleroderma.
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. 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.
33. 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.
34. 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).
35. A – Lyme disease (from tick bites while hiking) can cause a Bell’s palsy.
36. G – She’s Hepatitis B immune, but Hepatitis A isn’t mentioned. Hep A is transmitted through fecal-oral transmission, so when it comes to daycare, it means that if one kid gets it, they all get it.
37. D – Dark urine and pale stools mean direct hyperbilirubinemia (i.e. not physiologic jaundice, breast feeding or breast milk jaundice, G6PD deficiency, etc). With a subhepatic mass, you’re looking at a choledochal cyst: a rare, sad, congenital abnormality of the biliary system that leads to biliary obstruction, cirrhosis, and death if untreated. Some subtypes can be treated with surgery, others eventually require a liver transplant for survival.
38. D – If the MRI is normal, then prior traumatic hemorrhage has been ruled out. That leaves you with the vague “post-traumatic headache.”
39. H – Chronic diffuse persistent headache without any migrainous qualities is tension headache (the most common headache disorder).
40. F – If it sounds like a heart attack but the patient is totally fine, it’s a panic attack.
41. C – If all systems are constantly ramped up, it’s hyperthyroidism. Medical conditions that cause psychiatric complaints (e.g. hyperthyroidism and anxiety) are high-yield.

Block 2

42. 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.
43. E – Bilateral hilar adenopathy nearly always means sarcoidosis on board exams, especially in women in their 30-40s (and even more so if African-American). It’s a multisystem disease that can affect anything.
44. D – Mitral valve stenosis is a sequela of rheumatic heart disease that can lead to LAE and left-sided heart failure if left untreated.
45. E – Intermittent polyarthritis with positive ANA (sensitive but not specific) and anti-DNA (very specific) means lupus. You don’t even need the nonpainful mouth ulcers.
46. B – Episodic hypertension should make you think of pheochromocytoma (symptoms of headache or panic attacks etc. are common). Catecholamines are made in the adrenal medulla. The other malignancy to keep in mind with “panic-like” episodic flushing, headache, etc is carcinoid syndrome.
47. F – Weight loss and worsening lung symptoms in a smoker means lung cancer. Non-small cell is by far the most common variety.
48. E – Exfoliative and blistering drug reactions comes 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.
49. 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) and IVIG.
50. 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.
51. B – Irregular heavy menstrual bleeding in otherwise young healthy women is almost always due to anovulatory cycles. A normal pelvic ultrasound essentially rules out the rest.
52. 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).
53. 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.
54. A – PTSD symptoms that begin within 4 weeks of a traumatic event and last 4 weeks or less is acute stress disorder (ASD).
55. D – Super contagious super itchy rash of the hands and fingers (especially the webs!) is scabies. Viral exanthems do not localize to the waistband and hands.
56. E – The large cystic midline pelvic mass is her bladder, which is full of urine and must be decompressed emergently before any further workup is pursued.
57. D – Pain and swelling behind the ear means mastoiditis (remember the mastoid air cells?). The cause is nearly universally direct spread from otitis media.
58. 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).
59. 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.
60. 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, 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.
61. E – The only thing you do with things that look like primary melanoma is excise them completely.
62. B – Folic acid prevents neural tube defects. End stop.
63. H – Recurrent infection and 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).
64. A – RUQ pain and nausea after meals equals symptomatic cholelithiasis. The test of choice is RUQ sono to assess for stones.
65. 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.
66. C – Follow your ABCs. Tachycardia and hypotension mean severe volume loss necessitating aggressive intravenous fluid resuscitation.
67. E – Thrombocytopenia without antiplatelet antibodies or splenomegaly implies a platelet production problem (e.g. myelofibrosis). The only way to know what’s happening at the factory is a bone marrow biopsy.
68. D – Transillumination of a scrotal mass equals a hydrocele, which is due to a patent processus vaginalis.
69. 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.
70. D – Fever, AMS, and muscle rigidity in a patient on antipsychotics (aka ‘neuroleptics’) means neuroleptic malignant syndrome (NMS). Very rare, very dangerous.
71. B – Lumbar strain doesn’t require specific treatment or workup.
72. B – Diabetes get diabetic nephropathy. Don’t over-think things.
73. E – Pseudogout (calcium pyrophosphate deposition disease) is an inflammatory arthritis with a predilection for the knee that causes synovial calcifications.
74. 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.
75. E – LLQ pain with fever equals diverticulitis. The test of the choice is a CT scan of the abdomen with contrast.
76. A – Organ donation is a complex organizational dance, and the regional procurement organization manages the nitty-gritty aspects.
77. E – An acutely swollen painful great toe means gout. Gout is an inflammatory crystalline arthropathy. Aspiration reveals white cells and negatively-birefringent needle-shaped crystals.
78. 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).
79. B – Myocardial infarction causes heart muscle death (as the name implies). Lose enough muscle and you get systolic heart failure.
80. E – Abnormal vaginal bleeding in a woman over 35 requires an endometrial biopsy to rule out endometrial cancer.
81. 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, it’s how you address the C in ABC.
82. 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.
83. 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 antiplatelet therapy is contraindicated.
84. E – This question is comical. They even included the munchies.
85. B – Urinary symptoms (dysuria, urgency, frequency)  and positive urinalysis (leukocyte esterase and/or nitrite) without flank pain or systemic signs (fever, rigors, malaise, elevated white count) means simple acute cystitis. Add the other things, you get pyelonephritis.
86. G – Spermicidal jelly is a never a good thing in a USMLE question. It’s either causing chemical urethritis or implying totally inadequate contraception. Here, the usual work up was totally negative.

Block 3

87. 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.
88. 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 and rupture if not monitored.
89. D –The radiograph is showing complete collapse of the left lung (2/2 mucous plugging) with resultant severe mediastinal shift. Acute shift of this acutely 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.
90. 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.*
91. D – Abdominal pain is a common presenting complaint for DKA, which is a common presentation of new-onset type 1 diabetes. Note the glucose of 360.
92. C – Increasing pain after injury and casting, particularly with passive motion, means compartment syndrome. Compartment syndrome treatmentseems is barbaric, but a fasciotomy prevents neurovascular compromise.
93. B – Multiple lytic bony lesions equals multiple myeloma. Blastic/sclerotic lesions should make you think of metastatic prostate cancer (in men) and breast cancer (in women).
94. D – Atopic dermatitis (eczema) is the “itch that rashes.” It’s one leg of theallergic triad: asthma, allergic rhinitis, and atopic dermatitis. Treatment is with topical steroids and rigorous emollient therapy.
95. B – This patient has chronic (6 weeks) symptomatic hypotension while not coincidentally on three BP meds: a dieuretic, a beta blocker, and an ACE inhibitor. The most likely explanation and easiest/fastest intervention is to reduce her polypharmacy.*
96. E – Of the choices listed, only X-linked agammaglobulinemia causes recurrent respiratory bacterial infections. CGD results in multiple abscess-forming infections (predominately Staph aureus). B and C also cause recurrent viral infections in addition to bacterial disease.
97. A – Lisinopril and especially spironolactone (a K-sparing diuretic) both cause hyperkalemia. Renal failure (severe AKI or ESRD) is also a major cause of hyperkalemia, but not with the only mildly elevated Cr and BUN levels.
98. C – Obstructive sleep apnea (OSA) is diagnosed exclusively by polysomnography (aka a sleep study).
99. A – The most common cause of hypothyroidism in developed countries is Hashimoto’s thyroiditis. In developing countries, it’s iodine deficiency.
100. A – Proximal muscle weakness with skin findings means dermatomyositis.
101. 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.
102. 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.
103. F – Vasculitides like Wegener’s granulomatosis, microscopic polyangiitis, and others causes 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.
104. 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.*
105. A – Dermatomal rash means zoster. Immune insults, like chemotherapy, predispose to zoster flares.
106. A – It’s not clear that the glucose is a fasting value or not, but it’s clear the patient has insulin resistance. 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.
107. 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.
108. 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.
109. D – Microcytic anemia is essentially always iron-deficiency unless there is a reason to suspect a thalessemia. In this case, extensive surgery has removed nutrient absorbing small bowel.
110. 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.
111. D – Euvolemic hyponatremia means SIADH. Both brain and lung insults are common causes. Nonphysiologic secretion is “inappropriate,” of course.
112. B – Thick, white, and acidic means candidal vulvovaginitis (aka a yeast infection). Bacterial vaginosis typically only causes foul odor (and is alkaline, has positive whiff test, clue cells on wet mount, etc).
113. J – Sudden catastrophic neurological decline in patients with uncontrolled hypertension is likely due to a hemorrhagic stroke. Hypertensive hemorrhage is especially common in the basal ganglia, thalamus, pons, and cerebellum. The “hyperdense mass” is a big wad of blood.
114. D – If environmental, food, or exposure allergies ever include shortness of breath, then carry an epi-pen.
115. A – Lung cavities are made by tuberculosis but filled by aspergillus (the so-called “fungus ball”)
116. B – Acutely increased sputum production in a patient with COPD equals an exacerbation, which can be treated with steroid and antibiotics. The big-time smoking history automatically implies the COPD diagnosis; the ipratropium prescription cinches it.
117. C – The only test that can be performed between weeks 10-12 of gestation is chorionic villus sampling (CVS). It’s too early for amniocentesis, nuchal cord translucency, or triple/quad screening.
118. 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.
119. D – Polyps over 1 cm must be biopsied. This is especially concerning considering the blood loss anemia.
120. 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.
121. 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 evil, then it’s not conduct disorder.
122. B – Not fasting alters cholesterol studies, particularly serum triglycerides. You need real values prior to making any therapeutic interventions.
123. A – Stable patients who suffer blunt abdominal trauma get CT scans when stable. Contrast is needed to assess for solid organ injury (e.g. kidneys)
124. E – Don’t let the carpal tunnel history fool you. Numbness of the pinkie and half of the ring finger is ulnar entrapment (which happens at the elbow); carpal tunnel syndrome is the median nerve at the wrist (affecting thumb, index, middle, and half of the ring)
125. A – Cough is often the only sign of asthma. Exercise-induced asthma is exercise-induced asthma.
126. H – Congenital rubella is super uncommon (but very common on the boards): “blueberry muffin” rash, sensorineural deafness, eye abnormalities, and congenital heart disease. The mild rash in the mother is the historical clue.
127. A – Delivery at home is the red flag. Neonatal tetanus comes from inadequate cord hygiene, particularly when the cord is cut with a non-sterile instrument.
128. H – The most common inherited bleeding diasthesis is von Willebrand factor (VWF) deficiency, which is doubly true in women (as hemophilias are X-linked).
129. F – The presence of petechiae means low or grossly dysfunctional platelets (and not a factor coagulopathy). Coupled with low-grade fever, anemia (pale), splenomegaly, and lymphadenopathy, you should be thinking of leukemia (in this age group, ALL).
130. B – Cocaine (crack or the pricier variety) causes coronary vasospasm, which can cause myocardial infarction and acute heart failure.
131. A – Run of the mill myocardial infarction is caused by coronary artery thrombosis. Risk factors are HLD, HTN, DM, smoking, etc.

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