Explanations for the 2021 Official
Step 1 Practice Questions
04.17.21
This year’s set was updated in February 2021 (PDF here).
The asterisks (*) signify a new question, of which there are only 2
(#24 and 53). The 2020 set explanations and pdf are available here;
the comments on that post may be helpful if you have questions.
The less similar 2019 set is still available here for those looking for
more free questions, and even older sets are all listed here. The 2019
and 2020 sets, for example, differed by 36 questions (in case you
were curious).
Block 1
1. B – In addition to penicillin, the treatment paradigm for step
viridans endocarditis also includes the aminoglycoside
gentamicin, which binds to the 30S subunit and accelerates
bacterial clearing/decreases treatment duration.
2. A – Intermittent hyperbilirubinemia/jaundice in an otherwise
healthy individual is typical of Gilbert’s syndrome, which is
caused by the decreased activity of UDP
glucuronosyltransferase.
3. C – Acetylcholine increases after drug X, which is the same we’d
expect if drug X were a cholinesterase inhibitor.
4. C – The purpose of Rhogam is to bind to and remove the RhD
antigens so that the mother does not form an immune response
against the antigen in the fetus’ blood. It’s given to at-risk Rh-
moms at 28 weeks and at delivery.
, 5. A – Electrical alternans on boards means a big pericardial
effusion (and usually cardiac tamponade physiology). The heart
cannot fill properly, preload decreases, hypotension and
tachycardia ensue, fluid backup leads to elevated JVP.
Underlying etiology in this patient is renal failure (uremia).
6. C – Metformin is awesome. It decreases hepatic glucose
production, decreases intestinal absorption of glucose, and
improves insulin sensitivity by increasing peripheral glucose
uptake and utilization.
7. C – His leukocyte count is normal, so he’s not at risk for
opportunistic infection, but his platelets are low, placing him at
risk of bleeding. Petechiae are common in thrombocytopenia.
DVT (A) is the opposite problem, a thrombophilia. Joint
hemorrhage (hemarthrosis), nail bed hemorrhage, and frank
visceral hematomas are more commonly seen in hemophiliacs.
8. C – Serum sickness! A type III (immune complex)
hypersensitivity.
9. A – Narcotic use for acutely painful conditions is both
reasonable and important. (Very) short-term use (immediately
post-surgical) does not lead to long-term dependence (or so
people have thought…). And yes, even someone who uses
and/or is dependent on illicit drugs should also receive narcotics
to control pain.
10. B – Contract dermatitis is a type IV (T-cell mediated)
hypersensitivity. T-cell CD28 activation through binding CD80
(part of the B7 group) on the APC is the dominant interaction in
T-cell hypersensitivities/allergies.
11. A – Malonyl-CoA inhibits the rate-limiting step in the beta-
oxidation of fatty acid. Logically, resting muscle requires less
energy (and thus less need for fatty acid breakdown) than active
muscle.
12. C – This is obviously a clinical trial. If you know you are getting a
, drug, then you are not blinded: it’s an open-label trial. There is
no randomization as there is only a single treatment group.
13. B – Don’t let them blind you with this patient’s misery. The issue
of the day is that he has a DVT. That’s why he came to the ER in
the first sentence and what the ultrasound shows at the end.
Patients with cancer are hypercoagulable.
14. C – Leydig cells make testosterone. Leydig cell tumors aren’t
always physiologically active, but those that are can cause
masculinization. Granulosa cell tumors, on the other hand,
sometimes produce estrogen (which can lead to precocious
puberty in young girls but otherwise may be occult). Teratomas
are oddballs that typically have fat, hair, teeth, etc. Thecomas
will not be on your test. Ovarian carcinoid is highly unlikely to
show up on your test, but if it did, it would likely present with a
classic carcinoid syndrome.
15. E – Endothelial tight junctions’ permeability is increased in
response to injury and inflammation, allowing migration of white
blood cells and friends to the site of injury.
16. D – Pineal region tumors cause obstructive hydrocephalus due
to their proximity to the third ventricle. But in this case, we’re
being tested on pineal region tumors’ propensity to cause
Parinaud’s syndrome due to compression of the midbrain
tectum.
17. A – The CT scan showed “wedge-shaped areas of hypodensity,”
which are renal infarcts (wedge-shaped = vascular territory).
Renal infarcts are commonly caused by emboli from atrial
fibrillation, just like a fib can result in emboli in other areas like
the brain or limbs.
18. D – Hot tub folliculitis, it’s a thing. Classically pseudomonas.
19. A – As always, it’s almost better to ignore the pictures when
possible. This gentleman has a peptic ulcer, which we know is
caused predominately by H. pylori infection. H. pylori produces
Step 1 Practice Questions
04.17.21
This year’s set was updated in February 2021 (PDF here).
The asterisks (*) signify a new question, of which there are only 2
(#24 and 53). The 2020 set explanations and pdf are available here;
the comments on that post may be helpful if you have questions.
The less similar 2019 set is still available here for those looking for
more free questions, and even older sets are all listed here. The 2019
and 2020 sets, for example, differed by 36 questions (in case you
were curious).
Block 1
1. B – In addition to penicillin, the treatment paradigm for step
viridans endocarditis also includes the aminoglycoside
gentamicin, which binds to the 30S subunit and accelerates
bacterial clearing/decreases treatment duration.
2. A – Intermittent hyperbilirubinemia/jaundice in an otherwise
healthy individual is typical of Gilbert’s syndrome, which is
caused by the decreased activity of UDP
glucuronosyltransferase.
3. C – Acetylcholine increases after drug X, which is the same we’d
expect if drug X were a cholinesterase inhibitor.
4. C – The purpose of Rhogam is to bind to and remove the RhD
antigens so that the mother does not form an immune response
against the antigen in the fetus’ blood. It’s given to at-risk Rh-
moms at 28 weeks and at delivery.
, 5. A – Electrical alternans on boards means a big pericardial
effusion (and usually cardiac tamponade physiology). The heart
cannot fill properly, preload decreases, hypotension and
tachycardia ensue, fluid backup leads to elevated JVP.
Underlying etiology in this patient is renal failure (uremia).
6. C – Metformin is awesome. It decreases hepatic glucose
production, decreases intestinal absorption of glucose, and
improves insulin sensitivity by increasing peripheral glucose
uptake and utilization.
7. C – His leukocyte count is normal, so he’s not at risk for
opportunistic infection, but his platelets are low, placing him at
risk of bleeding. Petechiae are common in thrombocytopenia.
DVT (A) is the opposite problem, a thrombophilia. Joint
hemorrhage (hemarthrosis), nail bed hemorrhage, and frank
visceral hematomas are more commonly seen in hemophiliacs.
8. C – Serum sickness! A type III (immune complex)
hypersensitivity.
9. A – Narcotic use for acutely painful conditions is both
reasonable and important. (Very) short-term use (immediately
post-surgical) does not lead to long-term dependence (or so
people have thought…). And yes, even someone who uses
and/or is dependent on illicit drugs should also receive narcotics
to control pain.
10. B – Contract dermatitis is a type IV (T-cell mediated)
hypersensitivity. T-cell CD28 activation through binding CD80
(part of the B7 group) on the APC is the dominant interaction in
T-cell hypersensitivities/allergies.
11. A – Malonyl-CoA inhibits the rate-limiting step in the beta-
oxidation of fatty acid. Logically, resting muscle requires less
energy (and thus less need for fatty acid breakdown) than active
muscle.
12. C – This is obviously a clinical trial. If you know you are getting a
, drug, then you are not blinded: it’s an open-label trial. There is
no randomization as there is only a single treatment group.
13. B – Don’t let them blind you with this patient’s misery. The issue
of the day is that he has a DVT. That’s why he came to the ER in
the first sentence and what the ultrasound shows at the end.
Patients with cancer are hypercoagulable.
14. C – Leydig cells make testosterone. Leydig cell tumors aren’t
always physiologically active, but those that are can cause
masculinization. Granulosa cell tumors, on the other hand,
sometimes produce estrogen (which can lead to precocious
puberty in young girls but otherwise may be occult). Teratomas
are oddballs that typically have fat, hair, teeth, etc. Thecomas
will not be on your test. Ovarian carcinoid is highly unlikely to
show up on your test, but if it did, it would likely present with a
classic carcinoid syndrome.
15. E – Endothelial tight junctions’ permeability is increased in
response to injury and inflammation, allowing migration of white
blood cells and friends to the site of injury.
16. D – Pineal region tumors cause obstructive hydrocephalus due
to their proximity to the third ventricle. But in this case, we’re
being tested on pineal region tumors’ propensity to cause
Parinaud’s syndrome due to compression of the midbrain
tectum.
17. A – The CT scan showed “wedge-shaped areas of hypodensity,”
which are renal infarcts (wedge-shaped = vascular territory).
Renal infarcts are commonly caused by emboli from atrial
fibrillation, just like a fib can result in emboli in other areas like
the brain or limbs.
18. D – Hot tub folliculitis, it’s a thing. Classically pseudomonas.
19. A – As always, it’s almost better to ignore the pictures when
possible. This gentleman has a peptic ulcer, which we know is
caused predominately by H. pylori infection. H. pylori produces
