Tinea capitis (ringworm of the scalp)

Clinical forms

• Microsporum moth (Microsporum spp.) : large single or few + well-defined circular plaques + diameter 2-6 cm + broken hair a few mm from the scalp + dull + greyish hair + whitish scales + green-yellow fluorescence under the Wood's lamp (characteristic of Microsporum - not found with Trichophyton) + moderate pruritus
• Trichophytic moth (Trichophyton spp. - T. tonsurans) : small, multiple, irregular, poorly defined patches + grey scales + broken hair flush with the scalp (black dots - «black dot tinea» = stumps of broken hair visible as black dots in the follicle) + little or no Wood's lamp fluorescence + variable pruritus + sometimes mildly inflammatory picture resembling seborrheic dermatitis or scalp psoriasis → frequent cause of delayed diagnosis
• Inflammatory ringworm - Kérion de Celse : intense inflammatory reaction (hypersensitivity to fungal antigens) → erythematous + oozing + crusty + painful + suppurative plaque (pus draining from follicles on pressure) + alopecia of affected area + reactive cervical or sub-occipitaloccipital adenopathies + fever possible + may appear bacterial (impetiginized) but is mainly fungal + systemic antifungal treatment ++ + corticoids to reduce inflammation and prevent scarring alopecia
• Favus (favic moth - Trichophyton schoenleinii) : rare chronic form + scutules (cup-shaped yellowish crusts around the follicle) + characteristic mouse-like odor + scarring alopecia + endemic regions (North Africa + Middle East)

Pathogens by geography and source

Diagnosis

• Clinical examination + Wood's lamp : green-yellow fluorescence = Microsporum (darkroom examination) + absence of fluorescence = Trichophyton (majority in North America) → do not exclude tinea capitis on a negative Wood's lamp
• Mycological sampling : scalp scraping (scales + broken hair) + fresh state (KOH 10-20 %) → visualization of spores arranged in a sleeve around the hair shaft (ectothrix - Microsporum) or inside (endothrix - Trichophyton) + culture on Sabouraud medium (2-4 weeks) → species identification + antifungus if resistance suspected
• Mycological PCR : available in certain reference laboratories → rapid identification + higher sensitivity than culture
• Biopsy (kerion): rarely necessary + sometimes useful if there is any doubt about the diagnosis of a bacterial abscess or decalcifying folliculitis

Treatment

• Absolute rule : ORAL antifungal treatment is mandatory - topical antifungals alone (clotrimazole + miconazole + terbinafine cream) are INEFFECTIVE on tinea capitis because they do not penetrate the hair follicle where the fungi are located.
• Griseofulvin (historical reference treatment - particularly effective on Microsporum): 20-25 mg/kg/day (micronized) + or 10-15 mg/kg/day (ultramicronized) × 6-12 weeks (Microsporum) + or × 6-8 weeks (Trichophyton) + with a fatty meal (increased absorption) + effective on Microsporum canis ++ + less effective on T. tonsurans + monitoring: CBC + transaminases if prolonged treatment
• Terbinafine (reference treatment for T. tonsurans - North America) : 125 mg/d if 20 kg 40 kg × 4-6 weeks + more effective than griseofulvin on Trichophyton (meta-analyses) + less effective on Microsporum → adapt according to species identified
• Itraconazole (alternative - effective on both genera) : 5 mg/kg/day × 4-8 weeks + or pulsed regimen (5 mg/kg/day × 1 week/month × 2-3 cycles) + effective on Microsporum AND Trichophyton
• Fluconazole (less well-documented alternative) : 6 mg/kg/week × 8-12 weeks + or 6 mg/kg/day × 3-4 weeks
• Adjuvant antifungal shampoo (ketoconazole 2 % or selenium sulfide 2.5 %): 2-3 times/week × all treatment times + reduces spore load + reduces contagiousness + reduces transmission to contacts + DOES NOT replace oral treatment
• Kérion - specific treatment : systemic antifungal (terbinafine or griseofulvin depending on species) + prednisone 1 mg/kg/d × 1-2 weeks to reduce inflammation and prevent scarring + DO NOT incise-drain (aggravates) + DO NOT prescribe antibiotics alone (fungal, not bacterial cause)
• Contacts - decontamination measures : examine symptomatic contacts (brothers + sisters + classmates) + treat carrier contacts (possible asymptomatic carriage of T. tonsurans - prevalence 30-50 % in close contacts) with antifungal shampoo × 4-6 weeks + possibly oral antifungal if confirmed carriage + check and treat pet if Microsporum canis (veterinarian)
• Eviction from school: in Quebec - the child can return to school as soon as the oral antifungal treatment is initiated (no prolonged eviction) + but wearing a hat is not recommended (promotes heat + humidity) → information at school

Consult at Clinique Omicron

Clinique Omicron's specialized physicians and nurse practitioners (SPNs) diagnose tinea capitis by clinical examination (Wood's lamp + mycological sampling), prescribe the appropriate oral antifungal treatment for the suspected species (griseofulvin for Microsporum + terbinafine for T. tonsurans) + adjuvant antifungal shampoo, treat kerion with a systemic antifungal + corticosteroids, provide information on decontamination of contacts and pets, and specify conditions for returning to school. Consultations are available at several points of service in Quebec, as well as via telemedicine. To book an appointment, visit cliniqueomicron.ca.

The contents of this page are provided for information purposes only and do not replace the advice of a physician or dermatologist. Topical antifungals are insufficient to treat tinea capitis - systemic oral treatment is mandatory. Kerion should never be incised-drained or treated with antibiotics alone - it's a dermatological emergency requiring systemic antifungal + corticosteroid treatment.