Tinea Favosa
Tinea favosa, or favus, is the most severe form of superficial dermatophyte infection: a chronic condition and the most destructive type of tinea capitis for the scalp and hair follicles. Although it has become less common as living conditions and hygiene have improved, sporadic persistent cases still occur and are easily mistaken for scalp psoriasis, crusted impetigo or discoid lupus erythematosus. Its most serious complication is permanent destruction of the hair follicle stem cells in the bulge region, leading to irreversible scarring (cicatricial) alopecia and widespread scalp atrophy if medical treatment is delayed.
At Haute-Derma, our management of favus pursues two goals at once: eradicating the fungus that has penetrated deep into the hair shaft, and preserving or restoring as many non-scarred follicles as possible. We use fluorescence diagnosis, scalp dermoscopy (trichoscopy) and oral antifungal treatment combined with regenerative follicle care.
Causative Fungi and Pathogenesis
The main cause of tinea favosa is Trichophyton schoenleinii, an anthropophilic (human-adapted) dermatophyte. Less commonly, it can be caused by Trichophyton violaceum or Microsporum gypseum.
How Scutula Form: Unlike common forms of tinea capitis (such as gray-patch or black-dot types), T. schoenleinii invades the follicle and grows inside the hair shaft in an endothrix pattern without breaking the hair right away. At the follicle opening and in the surrounding horny layer, fungal hyphae combine with degenerated keratinocytes, broken-down neutrophils, sebum and dried serum to form a dense, sulfur-yellow, saucer- or cup-shaped crust called a scutulum (plural: scutula).
- Each scutulum has a depressed center, usually with a hair passing through it.
- Scutula are packed with living hyphae. As they merge, they form thick, honeycomb-like crusts that can cover the whole scalp and give off a strong, characteristic "mousy" odor as the fungus breaks down lipids and proteins.
How Scarring Alopecia Develops: Scutula press continuously on the follicle and the dermal papilla. At the same time, chronic granulomatous inflammation and fungal enzymes damage the follicular bulge, which houses the stem cells responsible for growing new hairs. Once the bulge becomes fibrotic and is replaced by scar tissue, the follicle permanently loses its ability to produce hair, leaving a smooth, shiny, atrophic bald patch.
Clinical Features and Differential Diagnosis
Tinea favosa progresses through three typical stages:
- Early stage: Red patches around the follicle openings with fine, yellowish scale, easily confused with seborrheic dermatitis or mild tinea capitis.
- Established stage: Classic sulfur-yellow scutula form. The hair loses its natural sheen and turns dull gray, dry and straw-like, but does not break off at the root; instead, it winds through the crusts. The scalp gives off a strong mousy odor.
- Late stage: As the scutula fall away, they leave thin, shiny, atrophic scalp with no follicle openings (atrophic scarring) and permanent bald patches.
Clinical Differential Diagnosis
| Tinea Favosa (Favus) | Kerion Celsi (Inflammatory Tinea Capitis) | Scalp Psoriasis |
|---|---|---|
| Sulfur-yellow, saucer-shaped scutula | Boggy, honeycomb-like swelling with pus draining from follicle openings | Thick red plaques with raised silvery-white scale |
| Dull gray hair, not broken at the root, passing through the center of the scutula | Fragile hair that comes out easily with gentle tweezer traction | Hair grows through the scale, no breakage, no scarring hair loss |
| Mousy odor | Foul smell of secondarily infected pus | None |
| Wood's lamp: dull pale green/grayish fluorescence | Wood's lamp: negative | Wood's lamp: negative |
| KOH 20%: endothrix hyphae + air bubbles inside the hair shaft | KOH 20%: hyphae/spores outside or inside the hair shaft | KOH 20%: negative |
How We Diagnose Favus at Haute-Derma
Wood's Lamp Examination: The scalp is examined under a 365 nm Wood's lamp in a fully darkened room. Favus caused by Trichophyton schoenleinii shows a characteristic dull, grayish pale-green fluorescence along the full length of infected hairs, which is clearly different from the bright green fluorescence of Microsporum canis.
Scalp Dermoscopy (Trichoscopy):
- Yellow scutula surrounding the follicle openings.
- Dull gray, slightly twisted, rope-like hairs.
- In late disease: complete loss of follicular openings (loss of follicular ostia), ivory-white areas of atrophic scar tissue and dotted dilated vessels.
KOH 20% Microscopy with Calcofluor White Fluorescent Staining:
- Part of a scutulum is scraped off and an affected hair is gently pulled.
- The sample is soaked in 20% KOH and gently warmed.
- Under the microscope:
- Favic chandeliers (antler-like hyphae): hyphae branching at sharp angles at the hair base, resembling a chandelier or deer antlers.
- Air bubbles inside the hair: as hyphae inside the hair shaft die and degenerate, they leave spaces filled with small air bubbles lined up along the shaft, a highly valuable microscopic clue that confirms T. schoenleinii.
Culture on Sabouraud Dextrose Agar (SDA): T. schoenleinii grows very slowly (2–3 weeks), forming ivory or cream-colored colonies with a heaped, folded, brain-like (cerebriform) surface that digs deep into the agar.
Comprehensive Treatment at Haute-Derma
Tinea favosa must be treated with a prolonged course of oral antifungals. Topical products cannot penetrate the dense scutula to reach the hair shaft and the base of the follicle.
Oral Antifungal Therapy (Essential):
- Terbinafine (our first choice at Haute-Derma):
- Adults: 250 mg once daily after a meal.
- Children: dosed by weight (10–20 kg: 62.5 mg/day; 20–40 kg: 125 mg/day; > 40 kg: 250 mg/day).
- Duration: at least 6–12 weeks (longer than for common tinea capitis).
- Itraconazole: 3–5 mg/kg/day (or 200 mg/day in adults), taken right after a fatty meal, for 6–8 weeks.
- Griseofulvin (traditional regimen): 15–20 mg/kg/day of the ultramicrosize form, taken continuously for 8–12 weeks.
Local Treatment and Removal of Scutula:
- Softening and lifting the scutula: 3–5% salicylic acid in olive oil or liquid paraffin is applied to the scalp and left on for 2–3 hours to soften the hard crusts, which are then washed away gently without making the scalp bleed.
- Medicated antifungal shampoo: ketoconazole 2% or ciclopirox olamine 1.5% shampoo three times a week, leaving the lather on the scalp for 5–10 minutes before rinsing, to reduce the number of infectious spores shed into the environment.
Follicle Recovery and Scar Management After Mycological Cure:
- Once KOH microscopy and fungal culture are negative twice in a row (2 weeks apart):
- We assess the density of surviving follicles with trichoscopy:
- Intact but weakened follicles: mesotherapy with hair growth peptides and biotin, plus platelet-rich plasma (PRP), to help the follicles recover.
- Fully scarred, atrophic bald patches: we discuss autologous hair transplantation (FUE) or scalp flap surgery once the infection has been fully controlled for at least 6 months.
