Fungal Diseases of the Skin

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Dermatophytosis

Tinea Versicolor
Candidiasis

Dermatophyte fungi reproduce by spore formation. They infect the stratum corneum, nails, and hair, inducing inflammation through delayed hypersensitivity or metabolic effects.

There are three genera:

Microsporum: Infect skin and hair.
Trichophyton: Infect skin, nails, and hair.
Epidermophyton: Infect skin and nails.

They can be classified based on their source and natural habitat:

Geophilic: Acquired from the soil.
Zoophilic: Acquired from animals.
Anthropophilic: Human-to-human transmission.

Clinical Presentation

Tinea (Latin: worm) denotes a fungal skin infection that often appears annular. The specific features depend on the site of infection.

Tinea Corporis (Trunk and Limbs): Characterized by single or multiple plaques with scaling and erythema, especially at the edges. Lesions slowly enlarge with central clearing, creating a ring pattern – hence the term 'ringworm.'
Tinea Cruris (Groin): More common in men and often seen in athletes ('jock itch'). It may spread to the upper thigh but rarely involves the scrotum. The advancing edge may be scaly, pustular, or vesicular.
Tinea Manuum (Hand): Typically appears as a unilateral, diffuse powdery scaling of the palm. T. rubrum is often the cause. It may coexist with Tinea pedis.
Tinea Capitis (Scalp/Hair): Caused by Trichophyton tonsurans or occasionally Microsporum canis.
Tinea Unguium (Nails):
Tinea Pedis (Athlete’s Foot):

Tinea Capitis

Particularly common in black and Hispanic children aged 4–14 years. Numerous confluent patches of alopecia develop, and patients may experience severe pruritus.

A severe inflammatory response produces elevated, boggy granulomatous masses known as kerions, which are often studded with pustules. Fever, pain, and regional adenopathy are common, and permanent scarring and alopecia may result.

The zoophilic organism M. canis or the geophilic organism Microsporum gypseum may also cause kerion formation.

Favus is a form of tinea capitis characterized by honeycomb scalp lesions with yellow crusts and scales. It is commonly associated with T. schoenleini.

Diagnosis

Microscopic examination of a KOH preparation of infected hair from the active border of a lesion discloses tiny spores surrounding the hair shaft in Microsporum infections and chains of spores within the hair shaft in T. tonsurans infections.
Fungal elements usually are not seen in scales.
A specific etiologic diagnosis of tinea capitis may be obtained by planting broken-off infected hairs on Sabouraud’s medium with reagents to inhibit the growth of other organisms. Such identification may require 2 weeks or more.

Treatment

Treatment for Tinea Capitis

Oral administration of griseofulvin microcrystalline (15 mg/kg/24 hr) is the recommended treatment for all forms of tinea capitis for 8 – 12 weeks; oral itraconazole can also be used.

Topical therapy alone is ineffective; it may be an important adjunct because it may decrease the shedding of spores.

For this purpose, vigorous shampooing with a 2.5% selenium sulfide or zinc pyrithione preparation is helpful. It is not necessary to shave the scalp.

Treatment for Tinea Corporis

Tinea corporis usually responds to treatment with one of the topical antifungal agents (e.g., miconazole, clotrimazole, econazole, ketoconazole, terbinafine, naftifine) applied twice daily for 2–4 weeks.

In unusually severe or extensive disease, a course of therapy with oral griseofulvin microcrystalline may be required for several weeks.

This common, chronic fungal infection of the stratum corneum is caused by the dimorphic yeast Malassezia furfur (Pityrisporum ovale, orbiculare).

Predisposing factors include a warm, humid environment, excessive sweating, occlusion, high plasma cortisol levels, immunosuppression, malnourishment, and genetically determined susceptibility.

The lesions vary widely in color: In whites, they typically are reddish brown, whereas in blacks they may be either hypopigmented or hyperpigmented.

The characteristic macules are covered with a fine scale and merge to form confluent patches, most commonly on the neck, upper chest, back, and upper arms.

There may be little or no pruritus.

Diagnosis of Pityriasis Versicolor

Examination with a Wood’s lamp discloses a yellowish-gold fluorescence.

A potassium hydroxide (KOH) preparation of scrapings is diagnostic, demonstrating groups of thick-walled spores and myriad short, thick, angular hyphae, resembling spaghetti and meatballs.

Skin biopsy, including culture and special stains for fungi (e.g., periodic acid–Schiff), are often necessary to make the diagnosis in cases of primarily follicular involvement.

Treatment of Pityriasis Versicolor

The disorder responds promptly to therapeutic agents, but because the organism responsible is a normal commensal, it recurs in predisposed people.

Agents used include:

Selenium sulfide suspension applied for 5–10 min each day for 2 wk;
25% sodium hyposulfite or thiosulfate lotion applied twice daily for 2–4 wk;
Lotions, ointments, or creams containing 3–6% salicylic acid twice daily for 2–4 wk;
Miconazole, clotrimazole, ketoconazole, or terbinafine cream twice daily for 2-4 wk.

Oral therapy:

Ketoconazole or fluconazole, 400mg, repeated in 1 wk;
Itraconazole, 200 mg/24 hr for 5–7 days.

Candida albicans is a ubiquitous commensal of the mouth and gastrointestinal tract which can produce opportunistic infections.

Predisposing factors include:

Moist and opposing skin folds
Obesity or diabetes mellitus
Immunosuppression
Poor hygiene
Humid environment
Use of broad-spectrum antibiotics

Types of Candidiasis

Genital Thrush: Commonly appears as an itchy, sore vulvovaginitis. White plaques adhere to inflamed mucous membranes and a white vaginal discharge may occur. Males develop similar changes on the penis. It can be spread by sexual intercourse.
Intertrigo: Super-infection with C. albicans, and often also with bacteria, gives a moist, glazed and macerated appearance to the submammary, axillary or inguinal body folds. The interdigital clefts are involved in wet workers who do not dry their hands properly.
Mucocutaneous Candidiasis: This rare, sometimes inherited disorder of immune deficiency starts in infancy. Chronic C. albicans intertrigo with nail and mouth infections is seen.
Oral Candidiasis: White plaques adhere to an erythematous buccal mucosa. Angular stomatitis may co-exist.
Systemic Candidiasis: Can occur in immunosuppressed patients. Red nodules are seen in the skin.

Management

General measures are important. Body folds are separated and kept dry with dusting powder.
Hands are dried carefully and oral hygiene improved. Systemic antibiotics may need to be stopped.
Magenta paint is useful for body folds, but is messy because of its colour.
Imidazoles are effective and available as creams, powders, and lotions.
For oral Candida, use amphotericin, nystatin, or miconazole as lozenges or gels.

Systemic Therapy

Bowel carriage may be reduced in recurrent candidiasis by oral nystatin. Itraconazole 100mg daily, or fluconazole (Diflucan) 50mg daily, but not griseofulvin, can be given as a short course for persistent C. albicans infections and in the long term for mucocutaneous candidiasis.

Vaginal candidiasis is treated by a single dose of 500 mg clotrimazole (Canesten) or 150 mg econazole (Gyno-Pevaryl) as a pessary, or with itraconazole or fluconazole by mouth.

Variant Differential Diagnosis

Genital Psoriasis, lichen planus, lichen sclerosus
Intertrigo Psoriasis, seborrheic dermatitis, bacterial secondary infection
Oral Lichen planus, epithelial dysplasia
Paronychia Bacterial infection, chronic eczema

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