HY lecture notes:
Malassezia furfur (tinea versicolor) is an incredibly HY spot-diagnosis on Steps 1 and 2CK (main image for this lecture).
It is a fungal infection that classically causes hypopigmentation on the trunk, back, and shoulders. This is caused by fatty acid breakdown in the skin.
Treatment is with topical selenium. Once again, super HY.
Scabies + lice (pediculosis) –> treat with permethrin.
USMLE will show you a picture of a guy’s hands that appear to be studded with red dots (linear burrows) + they’ll say he was living in a homeless shelter for four months + they will say topical antifungals were attempted but didn’t work; next best Tx? –> answer = permethrin.
Scabies-associated pyoderma (scabies + pus) is when a scabies lesions become infected with S. aureus or Group A Strep (S. pyogenes).
Pediculosis capitis = head lice; pediculosis corporis = body lice. Once again –> Tx with permethrin.
Tx for tinea capitis (cradle cap) = griseofulvin for patient only (one of the FM NBME Qs asks pt only vs patient + close contacts; answer is patient only).
Another tinea capitis Q wants “avoidance of hat sharing” as number-one way to prevent infection. They will have other answers like using anti-fungal shampoo, but “avoidance of hat sharing” is best way to prevent.
Tx for tinea corporis (ring worm) –> topical miconazole or clotrimazole.
Tx for tinea pedis (athletes foot) –> topical terbinafine or topical -azoles. USMLE won’t list both as answers for the same Q.
Tx for onychomycosis (fungal nail infection) –> oral terbinafine (6 weeks for fingernails; 12 weeks for toenails; USMLE won’t ask duration, but I just find that detail interesting + makes the treatment easier to remember).
USMLE wants you to know diabetes is a bigger risk factor for cutaneous candida than obesity –> they’ll say 48F + BMI of 67 + has red, moist, 8×12-cm elipse under one of her breasts; what’s the biggest risk factor? –> answer = “insulin resistance,” not obesity. This is exceedingly HY.
And it should be made clear that T1DM is equally a risk factor for cutaneous candidal infections; the USMLE just tends to ask the Q in obese patients with T2DM because they want to specifically assess you on knowing that dysglycemia/diabetes, period, is more important than obesity as a risk factor for cutaneous candida.
Chronic mucucutaneous candidiasis (CMC; more IM, but HY tangent) –> T cell dysfunction –> answer will be “defect in cell-mediated immunity” –> 17F + Hx of cutaneous candidal infections since childhood + 1-yr Hx of autoimmune thyroiditis + 2-yr Hx of T1DM; what’s the mechanism for her disease? –> answer = “defect in cell-mediated immunity,” or “T cell” (if they ask which cell is affected).
USMLE likes the concept of “autoimmune diseases to together,” and “autoimmune diseases and immunodeficiencies go together,” which is why the mention of the autoimmune thyroiditis and T1DM isn’t an accident; they’re essentially pushing on you the fact that she certainly has CMC.
Oropharyngeal candidiasis –> use nystatin mouthwash.
Esophageal candidiasis –> oral azole –> odynophagia in immunocompromised patient is esophageal candidiasis until proven otherwise.
Vaginal candidiasis –> topic nystatin –> if doesn’t work, go to oral azole –> nystatin is used first because the correct medicine is technically to do LFTs before giving an oral azole, whereas nystatin has shown efficacy and can be given right away.
