Fungal Infections of the Skin

Fungal infections can be classified into two types: superficial and deep (systemic) infections.
Superficial infections are restricted to the skin and its appendages, while deep infections are usually systemic in nature with occasional involvement of the skin.

Fungal infections can be caused by:
- Dermatophytes (e.g. microsporum, trichophyton, and epidermophyton)
- Yeasts (e.g. malassezia furfur and candida albicans)
Source of infection:
- From human (anthropophilic species)
- From animals (zoophilic species)
- Rarely, from soil (geophilic species)

The fungus changes from a budding yeast (Y) phase to a mycelial (M) phase, leading to a shift from a commensal state to a pathogenic state.

Mainly affects school children, more common in boys than girls.
Main causative fungi in Egypt are Trichophyton violaceum and Microsporum canis.
Clinical picture:
- Scaly type: single or multiple scaly patches, often circular in shape, with numerous broken-off hairs.
- Kerion (inflammatory type): caused by animal fungi, presented as boggy indurated swellings with crusting and loose hairs.
- Black-dot type: bald patches with formation of black dots as the affected hair breaks at the surface of the scalp.
- Favus: caused by Trichophyton schoenleinii, characterized by yellowish, cup-shaped crusts (scutula) and mousy odor.

Topical treatment: little effect, includes Whitfield's ointment, imidazoles, and allylamines
Systemic treatment:
- Griseofulvin: 10 mg/kg/day for at least 6 weeks and 8 weeks in favus
- Itraconazole, fluconazole, and terbinafine: only in selected cases

Commonly involves exposed skin, more common in children
Clinically: circular, sharply circumscribed, erythematous, and scaly with active edge (elevated and more inflamed than center)
Treatment: mild lesions, topical treatment for 2-4 weeks; extensive lesions, may require systemic antifungals

Mostly affects men on upper and inner surfaces of the thighs, especially in hot summer months
Clinical picture: small erythematous, scaly patch that spreads peripherally and partly clears in the center, edge is well defined with papules, vesicles, or pustules
Treatment: drying the lesions, specific topical, and oral antifungals

Most common fungal infection, more common in adult males
Predisposing factors: wearing tight shoes, communal showers, swimming baths, and hyperhydrosis
Clinical varieties:
- Interdigital variety: peeling, maceration, and fissuring affecting lateral toe clefts
- Squamous hyperkeratotic variety: very chronic and resistant to treatment, characterized by erythema and scaling
- Vesiculobullous variety: acute vesicular or bullous eruption may involve entire sole
Treatment: drying the feet thoroughly, antifungal powder on feet of susceptible persons, topical antifungals for mild cases, and systemic for extensive lesions

Nail plate becomes thickened, discolored, and cracked with accumulation of subungual hyperkeratosis
Treatment: oral antifungals, especially oral terbinafine, for 6 weeks in finger nails and for 12 weeks in toe nails

Mild, chronic fungal infection caused by Malassezia furfur
More common in tropical climates, with onset commonly in warmer months of the year
Clinical picture: sharply demarcated macule covered by fine branny scales, may coalesce to form large confluent areas and scattered oval patches
Treatment: topical antifungals, ketoconazole 2% shampoo, selenium sulphide 2-5% shampoo, and sodium hyposulphide 20% solution

Causative fungi: Candida albicans (normal inhabitant at various sites as gut, mouth, and vagina) or other species of Candida
Predisposing factors:
- Warmth, moisture, and maceration of skin
- Drugs: e.g. prolonged use of steroids, antibiotics, and immunosuppressives
- Chronic debilitating diseases: e.g. DM, lymphoma, and carcinoma
- AIDS
Clinical manifestations:
- Oral candidiasis (thrush): sharply defined patch of creamy, curd-like, white pseudomembrane
- Perleche (angular stomatitis): maceration with transverse fissuring of the angles of the mouth
- Candidal vulvovaginitis: labia are erythematous, moist, and macerated; cervix is hyperaemic, swollen, and eroded with some vesicles on its surface
- Candidal intertrigo: in skin folds, especially in obese individuals
- Napkin candidiasis: enhanced by maceration produced by wet diapers
- Candidal paronychia: cushion-like thickening of paronychial tissue, erosions of lateral borders of nail, gradual thickening and discoloration of nail plates, with development of transverse ridges