Dermatophytes

Clinical Presentation by Type and Body Site

• Scalp Ringworm (Tinea Capitis): This mainly affects children before puberty, because the fatty acid composition of sebum changes after puberty and becomes naturally antifungal. In the ectothrix type, caused by Microsporum canis, spores coat the outside of the hair shaft and damage the cuticle, producing large bald patches with hairs broken off 2–4 mm above the scalp and covered in gray scale. In the endothrix type, caused by Trichophyton tonsurans, spores fill the inside of the shaft, so hairs snap off right at the follicle opening, giving the typical "black dot" sign. Kerion celsi is a delayed hypersensitivity reaction to zoophilic fungi: a raised, soft, boggy plaque that discharges pus from the follicles, often with fever and tender neck lymph nodes.
• Facial and Beard Ringworm (Tinea Faciei and Tinea Barbae): Tinea barbae occurs on the chin and jaw of adult men, usually after contact with livestock or pets (T. verrucosum, T. mentagrophytes). It causes deep pustules around hair follicles; the beard skin becomes red, swollen and firm, and the hairs pull out painlessly. Tinea faciei affects the smooth skin of the face, varies widely in appearance and is often misdiagnosed as lupus erythematosus, atopic dermatitis or rosacea, especially when topical corticosteroids have blurred the edges of the rash.
• Body and Groin Ringworm (Tinea Corporis and Tinea Cruris): The classic lesion is a round or arc-shaped red patch that spreads outward; the center tends to clear and fade while the raised, sharply defined edge carries tiny blisters and scale. Trichophyton rubrum is the leading cause. In the groin, the rash spreads from the inguinal fold down the inner thighs and onto the buttocks, and itches intensely with sweating. When the fungus invades hair follicles deep in the dermis (often after shaving or steroid use), it becomes Majocchi granuloma, with dense red papules and deep pustules.
• Hand and Foot Ringworm (Tinea Manuum and Tinea Pedis): Athlete's foot takes three forms: interdigital (usually between the 4th and 5th toes, with white, macerated skin and painful fissures), vesicular (deep, very itchy blisters on the arch) and moccasin type (red, dry, thickened skin on the sole with fine scale along the skin creases). Tinea of the hand is often part of "two feet, one hand" syndrome: the patient has chronic T. rubrum infection of both soles but only one affected palm, the dominant hand used to scratch the infected feet.
• Dermatophyte Nail Infection (Tinea Unguium / Onychomycosis): The fungus invades the nail in four main patterns. Distal and lateral subungual onychomycosis (DLSO) is the most common: the fungus enters from the free edge into the nail bed, causing subungual hyperkeratosis, yellow-brown discoloration and separation of the nail from its bed. Superficial white onychomycosis (SWO) shows chalky white spots on the nail surface where T. mentagrophytes attacks the outer nail plate directly. In proximal subungual onychomycosis (PSO), the fungus enters at the proximal nail fold (often in immunocompromised patients). Total dystrophic onychomycosis (TDO) is the end stage, when the entire nail is destroyed, brittle and completely deformed.

Standardized Diagnosis of Dermatophyte Infections at Haute-Derma

To avoid confusing dermatophyte infection with other scaly skin conditions (such as psoriasis, pityriasis rosea or nummular eczema), Haute-Derma uses a multi-step microbiological workup:

• Advanced Dermoscopy:
  • Scalp: dermoscopy reveals hallmark signs of tinea capitis such as comma hairs, corkscrew hairs, boomerang-shaped hairs and scale encircling the follicle openings.
  • Nails: dermoscopy distinguishes fungal infection from nail trauma by a jagged (spike) pattern at the border between healthy and affected nail and longitudinal yellow-orange streaks.
• KOH Microscopy With Calcofluor White Fluorescent Staining:
  • Samples (scale scraped from the active edge, subungual debris or broken hairs) are treated with 10–20% KOH to dissolve keratin.
  • Under light microscopy, the lab looks for clear, septate hyphae branching at 45-degree angles and weaving between skin cells.
  • Calcofluor white binds specifically to chitin in the fungal cell wall. Under a fluorescence microscope the hyphae glow bright blue, raising diagnostic sensitivity above 95% even when very few hyphae are present.
• Culture and PCR Identification:
  • Samples are plated on Sabouraud dextrose agar (SDA) with chloramphenicol and cycloheximide and incubated at 25–30°C for 2–3 weeks.
  • Species are identified by colony appearance (front and reverse pigment) and by the features of macroconidia and microconidia under the microscope.
  • PCR identification is used when a drug-resistant strain (Trichophyton indotineae) is suspected or for complicated nail infections.

Personalized Treatment Plans at Haute-Derma

Treating dermatophyte infections means combining antifungal drugs, getting those drugs into keratin-rich tissue and clearing every reservoir of fungus:

• Topical Antifungal Therapy:
  • Allylamines: terbinafine 1% or naftifine 1% cream/gel. They are strongly fungicidal against dermatophytes because they block the enzyme squalene epoxidase. Apply 1–2 times daily for 2–4 weeks.
  • Newer azoles: sertaconazole 2% and luliconazole 1% build up high concentrations in the stratum corneum and also have an anti-inflammatory effect.
  • Medicated nail lacquers: amorolfine 5% (applied 1–2 times weekly) or ciclopirox 8% (applied daily) for mild DLSO/SWO affecting less than 50% of the nail plate without involvement of the nail matrix.
• Systemic Antifungal Therapy:
  • Oral terbinafine: the gold-standard choice for systemic dermatophyte treatment. Adult dose 250 mg/day.
    • Body and groin ringworm: 2–4 weeks.
    • Moccasin-type athlete's foot: 4–6 weeks.
    • Scalp ringworm (Trichophyton): 4–8 weeks.
    • Fingernails: 6 weeks; toenails: 12 weeks.
  • Oral itraconazole: the main alternative. For nail infections it is given as pulse therapy: 400 mg/day (in 2 divided doses) for 1 week, followed by 3 weeks off. Two pulses are given for fingernails and three for toenails.
  • Griseofulvin: the preferred option for children with scalp ringworm caused by Microsporum, at 15–20 mg/kg/day for 6–8 weeks (taken with a fatty meal to improve absorption).
• Combination and Advanced Therapies at Haute-Derma:
  • Managing terbinafine-resistant strains (Trichophyton indotineae): if a patient has not responded after 4 weeks of standard terbinafine, Haute-Derma switches to high-dose itraconazole (200–400 mg/day) with regular liver function monitoring.
  • Long-pulsed 1064 nm Nd:YAG laser for nail fungus: photothermal energy passes through the nail plate and raises the nail-bed temperature to 45–50°C, killing the fungus without damaging the nail matrix or causing pain.
  • Mechanical nail debridement (medical pedicure): a dedicated medical nail drill removes crumbling, diseased keratin so that topical drugs and laser energy reach the fungal focus directly.