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
• Ringworm of the scalp (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 — Kerion of Celsus 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 (ringworm — 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)

Pathogen agents 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
• Fungal sample collection: 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 treatment of choice - particularly effective against 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 (gold standard treatment for T. tonsurans — North America): 125 mg/day if 40 kg × 4–6 weeks + more effective than griseofulvin on Trichophyton (meta-analyses) + less effective on Microsporum → adapt according to the identified species
• Itraconazole (alternative - effective on both genders): 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
• Kerion — 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)
• School expulsion: 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 physician assistants and nurse practitioners (PAs/NPs) diagnose tinea capitis through clinical examination (Wood's lamp + mycological sampling), prescribe oral antifungal treatment appropriate for the suspected species (griseofulvin for Microsporum + terbinafine for T. tonsurans) plus an adjunctive antifungal shampoo, treat kerion with systemic antifungals + corticosteroids, inform about decontamination of contacts and pets, and specify conditions for returning to school. Consultations are available at several service points across Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.

The content of this page is for informational purposes only and is not a substitute for medical or dermatological advice. Topical antifungals are insufficient to treat tinea capitis—systemic oral treatment is mandatory. Kerion should never be incised-drained nor treated with antibiotics alone—it is a dermatological emergency requiring systemic antifungal treatment + corticosteroids.