Ringworm (Tinea): Fungal Causes, Types, and Transmission
Ringworm is a **dermatophyte** (keratin-loving fungus) infection of skin, hair, or nails — **not a worm**.
Causative Genera & Species
| Genus | Key Species | Common Infections | Primary Reservoir |
|---|
| Trichophyton | T. rubrum, T. mentagrophytes, T. tonsurans | Tinea corporis, cruris, pedis, capitis, unguium | Human (anthropophilic) |
| Microsporum | M. canis, M. audouinii | Tinea capitis, corporis | Cats/dogs (zoophilic) |
| Epidermophyton | E. floccosum | Tinea cruris, pedis | Human |
Transmission Routes
- Direct skin-to-skin (human/human, pet/human).
- Fomites: towels, clothing, combs, gym mats, shower floors.
- Soil (geophilic species) — rare.
Clinical Patterns
- Tinea corporis: Annular, scaly, advancing border, central clearing.
- Tinea cruris (jock itch): Groin, inner thighs; spares scrotum (vs. candida).
- Tinea pedis (athlete’s foot): Interdigital maceration, scaling, moccasin pattern.
- Tinea capitis: Scalp scaling, alopecia, black dots, kerion (inflammatory).
- Tinea unguium (onychomycosis): Thick, yellow, brittle nails.
Diagnosis & Treatment
- KOH prep (hyphae), fungal culture, PCR.
- Topical azoles/terbinafine (body, groin, foot) × 2–4 wks.
- Oral terbinafine/itraconazole/griseofulvin (scalp, nails, extensive) — 6 wks–12 mo.
- Hygiene: dry thoroughly, separate towels, treat pets.
Ringworm is contagious but curable. Early treatment prevents spread and scarring.
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