02/09/2026
Skin Fungal Infections
๐ Definition
๐ฌ Mechanism: tinea is a DERMATOPHYTE infection, and dermatophytes eat keratin, so they live in skin, hair, and nails
๐ง Mnemonic: the second word is Latin for the place, so capitis is head, corporis is body, cruris is groin, pedis is foot, unguium is nail
1๏ธโฃ Tinea Capitis (scalp)
๐ Presentation: a child with circular ALOPECIA, scaling, black dots from broken hairs, tender lymphadenopathy
๐ Tx: ORAL griseofulvin, because no cream reaches inside a hair shaft
โ ๏ธ Pearl: treat the patient only, and prevention is not sharing hats
2๏ธโฃ Tinea Corporis (body)
๐ Presentation: an enlarging scaly RING with CENTRAL CLEARING, hence ringworm
๐ฌ Source: often from an infected pet or farm animal
๐ Tx: topical azole such as clotrimazole
3๏ธโฃ Tinea Cruris (groin)
๐ Presentation: itchy rash spreading from the inguinal folds, known as jock itch
โ ๏ธ Pearl: unlike corporis it usually has NO central clearing, and it spares the sc***um
๐ Tx: topical azole, plus keeping the area dry
4๏ธโฃ Tinea Pedis (foot)
๐ Presentation: athlete's foot in three patterns, INTERDIGITAL (most common), MOCCASIN, VESICULAR
๐ Tx: topical terbinafine or azole
โ ๏ธ Pearl: fever with redness up the leg means Staph cellulitis on top, since fungus alone does not cause fever
5๏ธโฃ Tinea Unguium (nail)
๐ Presentation: onychomycosis, so thickened yellow brittle nails
๐ Tx: ORAL terbinafine, because nothing topical penetrates the nail plate
โ ๏ธ Pearl: preferred over griseofulvin, which induces cytochrome P-450
6๏ธโฃ Tinea Versicolor (the impostor)
๐ฌ Cause: Malassezia, a YEAST, so despite the name it is not a dermatophyte
๐ฌ Mechanism: it splits skin lipids into acids that inhibit tyrosinase, so less melanin
๐ Presentation: hypopigmented or pink patches on the trunk, LESS itchy, worse in humid summer
๐ Dx: spaghetti and meatballs on microscopy
๐ Tx: selenium sulfide or a topical azole