SN7 SHORT NOTE 5M

Write a short note on dermatophyte (tinea) infections.

General Medicine · Final Professional

Definition & Aetiology

Dermatophytoses are superficial fungal infections of keratinised tissue — skin, hair and nails — caused by three genera: Trichophyton, Microsporum and Epidermophyton. They digest keratin using keratinases and do not invade living tissue; the inflammation is a host response to fungal antigen.

Predisposing factors: heat and humidity (making it extremely common in India), sweating, occlusive footwear and synthetic clothing, obesity with skin folds, diabetes mellitus, immunosuppression, sharing of towels and clothing, and — increasingly important — misuse of topical corticosteroid-containing combination creams.

Clinical Types

Type	Site	Features
Tinea corporis	Trunk, limbs	Annular plaque with raised, scaly, active advancing edge and central clearing; itchy
Tinea cruris	Groin, inner thigh	Advancing scaly edge; spares the scrotum (unlike candidiasis, which involves it)
Tinea pedis	Feet	Interdigital maceration and fissuring (athlete's foot), or moccasin-type dry scaling of soles
Tinea capitis	Scalp	Children; scaly patches with hair loss and broken hairs; kerion = boggy inflammatory mass; may scar
Tinea unguium (onychomycosis)	Nails	Distal subungual thickening, yellow discoloration, onycholysis, subungual debris
Tinea manuum	Hand	Often unilateral with dry scaling — the "two feet, one hand" pattern
Tinea incognito	Any	Modified by topical corticosteroid — loss of the raised scaly margin, extensive, atypical, with pustules and telangiectasia

Diagnosis

KOH mount of skin scraping, hair or nail clipping — shows septate branching hyphae; the essential bedside investigation.
Fungal culture on Sabouraud dextrose agar — identifies the species; takes 2–4 weeks.
Wood's lamp — green fluorescence in *Microsporum* tinea capitis (most Trichophyton species do not fluoresce).
Dermoscopy — comma and corkscrew hairs in tinea capitis.
Screen for diabetes in extensive or recurrent disease.

Management

Topical (localised disease): terbinafine, clotrimazole, ketoconazole or luliconazole cream applied to the lesion and 2 cm beyond the margin, continued for 2 weeks after clinical clearance to prevent relapse.

Systemic — indicated for:

Tinea capitis and tinea unguium — always, because topical agents do not penetrate hair and nail adequately.
Extensive or recurrent disease, tinea incognito, immunosuppression, or failure of topical therapy.
Agents: terbinafine, itraconazole, fluconazole and griseofulvin (griseofulvin remains standard for *Microsporum* tinea capitis in children). Duration is weeks for skin, and months for nails.

General measures — as important as drugs:

Treat all affected family members simultaneously; household spread sustains reinfection.
Keep the area dry; use loose cotton clothing; dry skin folds carefully after bathing; avoid sharing towels, combs and footwear; wash and sun-dry clothing and bedding.
Treat concurrent tinea pedis and onychomycosis, which act as reservoirs for repeated reinfection of the groin and trunk.

DANGER / REMEMBER

Never treat tinea with a corticosteroid-containing combination cream. These over-the-counter preparations produce rapid symptomatic relief but suppress local immunity, causing tinea incognito — extensive, atypical, steroid-modified disease that is far harder to treat. Recalcitrant and recurrent dermatophytosis is now a major problem in India, attributed largely to this practice together with irregular and inadequate courses of treatment. Explicitly warn patients against these creams.

NEEDS VERIFICATION

Systemic antifungal doses and durations, and current Indian recommendations for recalcitrant dermatophytosis — this area has changed substantially in recent years; confirm before publication.

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