MEHLMANMEDICAL
HY USMLE REVIEW
PART II
, MEHLMANMEDICAL.COM
YouTube
@mehlmanmedical
Instagram
@mehlman_medical
MEHLMANMEDICAL.COM 2
, MEHLMANMEDICAL.COM
HY USMLE Review – Part II
- “Hot feels cold; cold feels hot” (temperature dysesthesia) à ciguatera toxicity à toxin blocks sodium
channels à caused by consumption of reef fish (mahimahi, Spanish mackerel, etc.)
- Pt with no prior Hx of atopy/asthma + eats meaty fish in sketch location (e.g., Bali) + develops
dyspnea + allergic-like reaction à answer = scombroid, not seafood allergy à histidine decarboxylase
in decaying fish convert histidine to histamine à allergic-like reaction (often misdiagnosed as allergy)
- Pt gets allergic-like reaction after eating shellfish à answer = shellfish allergy, not scombroid
(students get all trigger-happy about scombroid after learning about something new, weird, and cool,
but if on the USMLE they say shellfish, it’s shellfish allergy, not scombroid)
- Vomiting a few hours after eating meat à S. aureus preformed heat-stable toxin
- Vomiting (or any unusual Sx like bloody diarrhea) + eating custards, creams, potato salad à answer =
S. aureus preformed HS toxin à the type of food in this scenario “wins” over the weird bloody
diarrhea finding à bear in mind typical bloody-diarrhea-inducing gram (-) rods like EHEC, Yersinia
enterocolitica, Campylobacter, Shigella, Salmonella have ~1-3-day incubation period) à iow, if you
get sick on the scale of hours from food, S. aureus preformed toxin is likely
- Tx of otitis externa à topical ciprofloxacin + hydrocortisone drops
- Prophylaxis for otitis externa (i.e., in someone with continued water exposure, like crew) à topical
alcohol-acetic acid drops
- Tx for cerumen buildup à carbamide peroxide drops
- Most common cause of otitis externa à Pseudomonas
- Otitis externa + mastoiditis à malignant otitis externa
- Mx of malignant otitis externa à CT or MRI of temporal bone because pus collection is common; if
don’t rule out fluid collection and drain it appropriately, can cause brain abscess; this is on one of the
pediatric NBME forms, where the answer was CT of the temporal bone in a two-year-old, which is an
outrageous dose of radiation for a kid, but it’s the answer on the form; in UW for 2CK, they didn’t list
CT, but had MRI and x-ray as answers, and MRI was correct; apparently x-ray is insufficient;
mastoiditis will classically present in kid with a pinna that’s displaced upward and outward, often with
him or her pulling on it bc of the pain.
MEHLMANMEDICAL.COM 3
HY USMLE REVIEW
PART II
, MEHLMANMEDICAL.COM
YouTube
@mehlmanmedical
@mehlman_medical
MEHLMANMEDICAL.COM 2
, MEHLMANMEDICAL.COM
HY USMLE Review – Part II
- “Hot feels cold; cold feels hot” (temperature dysesthesia) à ciguatera toxicity à toxin blocks sodium
channels à caused by consumption of reef fish (mahimahi, Spanish mackerel, etc.)
- Pt with no prior Hx of atopy/asthma + eats meaty fish in sketch location (e.g., Bali) + develops
dyspnea + allergic-like reaction à answer = scombroid, not seafood allergy à histidine decarboxylase
in decaying fish convert histidine to histamine à allergic-like reaction (often misdiagnosed as allergy)
- Pt gets allergic-like reaction after eating shellfish à answer = shellfish allergy, not scombroid
(students get all trigger-happy about scombroid after learning about something new, weird, and cool,
but if on the USMLE they say shellfish, it’s shellfish allergy, not scombroid)
- Vomiting a few hours after eating meat à S. aureus preformed heat-stable toxin
- Vomiting (or any unusual Sx like bloody diarrhea) + eating custards, creams, potato salad à answer =
S. aureus preformed HS toxin à the type of food in this scenario “wins” over the weird bloody
diarrhea finding à bear in mind typical bloody-diarrhea-inducing gram (-) rods like EHEC, Yersinia
enterocolitica, Campylobacter, Shigella, Salmonella have ~1-3-day incubation period) à iow, if you
get sick on the scale of hours from food, S. aureus preformed toxin is likely
- Tx of otitis externa à topical ciprofloxacin + hydrocortisone drops
- Prophylaxis for otitis externa (i.e., in someone with continued water exposure, like crew) à topical
alcohol-acetic acid drops
- Tx for cerumen buildup à carbamide peroxide drops
- Most common cause of otitis externa à Pseudomonas
- Otitis externa + mastoiditis à malignant otitis externa
- Mx of malignant otitis externa à CT or MRI of temporal bone because pus collection is common; if
don’t rule out fluid collection and drain it appropriately, can cause brain abscess; this is on one of the
pediatric NBME forms, where the answer was CT of the temporal bone in a two-year-old, which is an
outrageous dose of radiation for a kid, but it’s the answer on the form; in UW for 2CK, they didn’t list
CT, but had MRI and x-ray as answers, and MRI was correct; apparently x-ray is insufficient;
mastoiditis will classically present in kid with a pinna that’s displaced upward and outward, often with
him or her pulling on it bc of the pain.
MEHLMANMEDICAL.COM 3
