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HY USMLE REVIEW
PART III
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HY USMLE Review – Part III
- 72F + radical mastectomy 25 years ago + hard, raised purple lesions above the elbow; Dx? à
lymphangiosarcoma (Stewart-Treves syndrome) à you don’t have to agree that it’s HY, but it’s asked
on the NBME à caused by chronic lymphatic insufficiency classically years after radical mastectomy.
- Neonate + spongy 1-cm red lesion on the chest; Dx? à strawberry hemangioma
- Strawberry hemangioma Tx? à don’t treat; will grow slightly then regress spontaneously over a few
years
- Neonate + large vascular lesion on the leg + thrombocytopenia; Dx? à Kasabach-Merritt syndrome
(aka hemangioma with thrombocytopenia) à this is on the pediatric 2CK forms three times asked in
different ways; students always say wtf and I have to explain that, yes, it’s weird, but it’s HY for some
magical reason; this is not a strawberry hemangioma and requires surgical Tx.
- Neonate + large vascular lesion on the leg + thrombocytopenia; what is the cause of the
thrombocytopenia? à answer = “platelet sequestration.” I’ve memorized this from the NBMEs à
similar to splenomegaly, which can cause thrombocytopenia from sequestration within the red pulp,
the implication that the large vascular lesion of KMS is that platelets simply get caught within it.
- “Cherry red blood/lips” à CO poisoning
- “Brown blood” or “chocolate blood” à methemoglobinemia
- Kid with brown blood and they ask you the mechanism (answers are “upregulation of anti-proteinase
2” or “deficiency of cytochrome reductase B5”) à answer = deficiency of cytochrome reductase B5;
this is on the USMLE. I’m not fucking with you. And if you Wiki it, you’ll see clear as day that they talk
about congenital methemoglobinemia due to deficiency of cytochrome reductase B5.
- 22M + violaceous papules in a temporal distrubtion à answer = Sturge-Weber syndrome; student
says “wtf? I thought that was associated with Port wine stain birthmark.” Yeah, if we take a trip back
to kindergarten, but you need to know it can present as cutaneous papules in a trigeminal nerve
distribution.
- 44M alcoholic + winter + they show a pic of his feet and they’re red; what electrolyte are we most
worried about upon rewarming them à answer = hyperkalemia à alcoholics are notably susceptible
to rhabo (ultra HY on the USMLE) à rhabdo causes myoglobin release, which is nephrotoxic and can
cause acute tubular necrosis (potassium goes up); even if the patient doesn’t get full-blown rhabdo
MEHLMANMEDICAL.COM 3
HY USMLE REVIEW
PART III
, MEHLMANMEDICAL.COM
YouTube
@mehlmanmedical
@mehlman_medical
MEHLMANMEDICAL.COM 2
, MEHLMANMEDICAL.COM
HY USMLE Review – Part III
- 72F + radical mastectomy 25 years ago + hard, raised purple lesions above the elbow; Dx? à
lymphangiosarcoma (Stewart-Treves syndrome) à you don’t have to agree that it’s HY, but it’s asked
on the NBME à caused by chronic lymphatic insufficiency classically years after radical mastectomy.
- Neonate + spongy 1-cm red lesion on the chest; Dx? à strawberry hemangioma
- Strawberry hemangioma Tx? à don’t treat; will grow slightly then regress spontaneously over a few
years
- Neonate + large vascular lesion on the leg + thrombocytopenia; Dx? à Kasabach-Merritt syndrome
(aka hemangioma with thrombocytopenia) à this is on the pediatric 2CK forms three times asked in
different ways; students always say wtf and I have to explain that, yes, it’s weird, but it’s HY for some
magical reason; this is not a strawberry hemangioma and requires surgical Tx.
- Neonate + large vascular lesion on the leg + thrombocytopenia; what is the cause of the
thrombocytopenia? à answer = “platelet sequestration.” I’ve memorized this from the NBMEs à
similar to splenomegaly, which can cause thrombocytopenia from sequestration within the red pulp,
the implication that the large vascular lesion of KMS is that platelets simply get caught within it.
- “Cherry red blood/lips” à CO poisoning
- “Brown blood” or “chocolate blood” à methemoglobinemia
- Kid with brown blood and they ask you the mechanism (answers are “upregulation of anti-proteinase
2” or “deficiency of cytochrome reductase B5”) à answer = deficiency of cytochrome reductase B5;
this is on the USMLE. I’m not fucking with you. And if you Wiki it, you’ll see clear as day that they talk
about congenital methemoglobinemia due to deficiency of cytochrome reductase B5.
- 22M + violaceous papules in a temporal distrubtion à answer = Sturge-Weber syndrome; student
says “wtf? I thought that was associated with Port wine stain birthmark.” Yeah, if we take a trip back
to kindergarten, but you need to know it can present as cutaneous papules in a trigeminal nerve
distribution.
- 44M alcoholic + winter + they show a pic of his feet and they’re red; what electrolyte are we most
worried about upon rewarming them à answer = hyperkalemia à alcoholics are notably susceptible
to rhabo (ultra HY on the USMLE) à rhabdo causes myoglobin release, which is nephrotoxic and can
cause acute tubular necrosis (potassium goes up); even if the patient doesn’t get full-blown rhabdo
MEHLMANMEDICAL.COM 3
