DISEASE
ORGANISM · SPREAD
CLINICAL PICTURE
DIAGNOSIS · TREATMENT
Trichophyton tonsurans (most US), Microsporum; children, shared combs
Scaly patches of hair loss with broken hairs ("black dots"); posterior cervical nodes; kerion (boggy, inflamed mass)
Oral therapy needed (griseofulvin, terbinafine) — topical doesn't reach the follicle
Contact with people (wrestlers), pets (Microsporum canis)
Annular, scaly, itchy plaque with raised border and central clearing ("ringworm")
Topical azoles or terbinafine
Heat, moisture, obesity; often from own feet
Itchy red groin rash with sharp border, spares scrotum
Candida intertrigo involves scrotum + satellite lesions
Locker rooms, occlusive shoes
Interdigital maceration and scale; "moccasin" distribution; vesicles
Portal for cellulitis
Onychomycosis (tinea unguium)
T rubrum; older adults, diabetes
Thick, yellow, crumbly nails with subungual debris
Confirm with KOH/culture · oral terbinafine (check LFTs)
Topical steroid applied to tinea
Less scaly, spreading, atypical rash
Stop steroid, treat fungus
Malassezia (lipophilic yeast) makes azelaic acid → ↓ tyrosinase
Hypo- or hyperpigmented scaly macules on chest/back; don't tan
KOH: short hyphae + yeast ("spaghetti and meatballs") · selenium sulfide, ketoconazole
Malassezia-associated inflammation
Greasy scale on scalp, eyebrows, nasolabial folds; infant cradle cap; severe in HIV, Parkinson
Ketoconazole shampoo
Lipid-rich TPN in neonates
Line sepsis
Needs lipid-supplemented media
UV light
Some Microsporum fluoresce green; Malassezia yellow-green; erythrasma (Corynebacterium) coral-red
T tonsurans doesn't fluoresce