Key Facts

Tinea infections are superficial dermatophyte infections named by the body site affected. They are extremely common and usually straightforward to diagnose and treat. Tinea capitis and onychomycosis require systemic antifungal treatment.

Epidemiology

• Tinea pedis: most common (~15–25% of population)
• Tinea capitis: increasing in UK; predominantly affects children aged 3–14; T. tonsurans now the most common cause
• Onychomycosis: affects ~10% of adults; increases with age
• Tinea corporis and cruris: common in young adults, athletes

Aetiology

• T. rubrum: most common dermatophyte globally; causes tinea pedis, corporis, cruris, unguium
• T. tonsurans: now the commonest cause of tinea capitis in UK (anthropophilic)
• M. canis: zoophilic — acquired from cats/dogs; causes tinea corporis, capitis
• E. floccosum: tinea cruris
• Risk factors: warm/moist environment, communal facilities (pools, gyms), diabetes, immunosuppression, obesity

Pathophysiology

• Dermatophytes produce keratinases → digest keratin in stratum corneum, hair, nails
• Fungal hyphae spread centrifugally in skin → annular lesion with active advancing edge
• Inflammatory response at the periphery → raised, erythematous, scaly border
• Central clearing as immune response controls infection behind the advancing front

Tinea Corporis (Body)

• Annular ('ring-shaped') erythematous plaque
• Raised, scaly advancing edge with central clearing
• Single or multiple lesions
• Can affect any body site

Tinea Pedis (Feet)

• Interdigital: maceration, peeling between toes (especially 4th/5th web space)
• Moccasin-type: diffuse, dry, scaly erythema on soles and lateral feet
• Vesiculobullous: inflammatory vesicles/bullae on instep

Tinea Cruris (Groin)

• Erythematous, scaly rash extending from groin crease to inner thighs
• Well-defined advancing edge
• Spares the scrotum (distinguishing feature from Candida intertrigo)
• Often coexists with tinea pedis

Tinea Capitis (Scalp)

• Scaly patches with hair loss in children
• Broken hairs, black dot pattern (T. tonsurans)
• Kerion: severe inflammatory response — boggy, tender mass with pustules; may cause permanent scarring alopecia
• Posterior cervical lymphadenopathy

Onychomycosis (Nails)

• Distal lateral subungual: yellow/white discolouration from free edge; most common
• Nail thickening, crumbling, onycholysis
• Toenails more commonly affected than fingernails

Red Flags

• Kerion — needs urgent systemic treatment
• Rapidly spreading in immunocompromised
• Tinea incognito — atypical appearance, ask about steroid use

Bedside

• Skin scraping (from advancing edge): KOH preparation — branching septate hyphae
• Hair pluck (tinea capitis): broken/affected hairs for microscopy and culture
• Nail clipping (onychomycosis): send for microscopy and culture — confirm before systemic treatment
• Wood's lamp: Microsporum spp. fluoresce green; T. tonsurans does NOT fluoresce

Microbiology

• Fungal culture on Sabouraud's agar: species identification; takes 2–6 weeks
• Dermatophyte PCR: available in some centres — rapid results

Bloods

• LFTs: before systemic antifungals (terbinafine, itraconazole)
• Blood glucose/HbA1c: recurrent infection — screen for diabetes

Special Tests

• Dermoscopy of scalp: comma hairs, corkscrew hairs (tinea capitis)
• Nail plate biopsy with PAS stain: if culture negative but clinical suspicion high

Non-Pharmacological

• Hygiene: wash and dry feet thoroughly; dry between toes; change socks daily
• Avoid sharing: towels, combs, shoes
• Athlete's foot: antifungal foot powder, breathable footwear
• Contact tracing: tinea capitis — household contacts may be asymptomatic carriers

Pharmacological — Localised Skin Infection

• Terbinafine 1% cream OD for 1–2 weeks: first-line for limited dermatophyte infection
• Clotrimazole 1% cream BD for 2–4 weeks: alternative
• Miconazole 2% cream BD: alternative

Pharmacological — Systemic (Scalp, Nails, Widespread)

Tinea capitis:

• Terbinafine 250 mg OD (adults; weight-based dosing in children): 4 weeks for Trichophyton, 6–8 weeks for Microsporum
• Griseofulvin 500 mg–1 g OD (adults): alternative, especially for Microsporum; 6–8 weeks
• Adjunctive antifungal shampoo (ketoconazole 2%): reduces spore shedding; does not treat infection alone

Onychomycosis:

• Terbinafine 250 mg OD: 6 weeks (fingernails), 12 weeks (toenails); cure rate ~70–80%
• Itraconazole pulse therapy: 200 mg BD for 1 week/month — 2 pulses (fingers), 3 pulses (toes)
• Amorolfine 5% nail lacquer: adjunct for mild, distal involvement

Kerion:

• Systemic antifungal (terbinafine) PLUS short course oral prednisolone 0.5–1 mg/kg to reduce inflammation and scarring

Referral Criteria

• Dermatology: treatment failure, diagnostic uncertainty, widespread infection
• Paediatrics: tinea capitis with kerion
• Podiatry: recurrent onychomycosis

• Tinea corporis/cruris/pedis: excellent with topical treatment; recurrence related to ongoing risk factors
• Tinea capitis: good with systemic treatment; kerion may cause permanent scarring alopecia
• Onychomycosis: cure rate ~70–80% with terbinafine; relapse/reinfection ~20–25%
• Tinea incognito: resolves once steroids stopped and antifungal commenced
• Immunocompromised: chronic, relapsing course; may need prolonged treatment

Tinea Infection Summary

Topical vs Systemic Antifungal Indications