Superficial Mycoses: Pityriasis & Tinea Nigra

Superficial Mycoses

• Infections limited to the outermost layers of skin and hair.
• Includes skin and hair infections.

Infection of Skin

• Pityriasis versicolor and tinea nigra are common causes.

Infection of Hair

• Black and white piedra are causative agents.

Pityriasis Versicolor (Tinea Versicolor)

• Chronic superficial fungal infection affecting the uppermost horny layer of the epidermis.
• Primarily affects the chest, abdomen, upper limbs, and back, but can appear anywhere on the skin.
• Infection results in loss of skin pigmentation, leading to hypo- or hyperpigmentation.
• Caused by yeast flora known as Pityrosporum orbicularis.
• Treatment includes topical selenium sulfide, oral ketoconazole, or oral itraconazole.

Tinea Nigra

• Localized infection of the stratum corneum, especially on the palms.
• Produces black or brownish macular lesions.
• Clinical findings include brownish maculae on palms, fingers, and the face.
• Etiology is linked to Hortae (Exophiala) werneckii.
• Management includes topical salicylic acid or tincture of iodine.

Piedra

• Fungal infection of the hair, characterized by firm, irregular nodules along the hair shaft.
• Black piedra is caused by Piedraia hortae.
• White piedra is caused by Trichosporon beigelii.

Black Piedra

• Fungal infection of the scalp hair.
• Presence of black, hard nodules, up to 1 mm in diameter, mainly on scalp hairs is a key characteristic.
• Treatment includes topical salicylic acid and azole creams.

White Piedra

• A fungal infection of facial, axillary, or genital hair.
• Characterized by soft, white to yellowish nodules loosely attached to the hair.
• Shaving and azoles are effective treatments.

Cutaneous Mycoses (Dermatophytoses)

• Infections extending deeper into the epidermis, involving invasive hair and nail disease.
• This includes infections of skin, hair, and nails caused by dermatophytes.
• Dermatomycosis is a more general term for any skin disease caused by a fungus.
• Dermatophytosis is a fungal infection of keratinous structures by dermatophytes.
• Tinea is equivalent to dermatophytosis.

Classification of Dermatophytes

• Trichophyton species infect hair, skin, or nails.
• Microsporum species infect only hair and skin.
• Epidermophyton attacks the skin and nails, not the hair.

Etiological Classification of Dermatophytosis

• Anthropophilic species transmit from human to human, such as Epidermophyton flocosum.
• Zoophilic species transmit from animal to human, such as Microsporum canis.
• Geophilic species occur via spores found in soil, such as Microsporum gypseum.

Clinical Classification of Dermatophytosis

• Includes Tinea capitis, corporis, cruris, unguium, barbae, manuum, and pedis.

Tinea Capitis

• Fungal infection of the scalp and hair.
• Includes three forms of hair involvement such as endothrix, ectothrix, and favic type.
• Endothrix involves abundant fungus growth inside the hair shaft.
• Ectothrix involves spores surrounding the hair shaft from the outside.
• Favic type involves some fungal mycelia present inside the hair shaft with air.

Tinea Corporus

• Dermatophyte infection of the glabrous skin (trunk, back, dorsum of the hand).

Tinea Cruris

• Ringworm infection of the groin (jock itch).

Tinea Unguium

• Fungal infection of the nail of the hand.

Tinea Barbae

• Fungal infection of the beard and mustache skin area in males.

Tinea Manuum

• Fungal infection of the palm of the hand and interdigital areas.

Tinea Pedis

• Ringworm infection of the foot (athlete's foot).

Epidemiology

• Affects children, adults, males, and females, with higher incidence in school-age children.
• Found worldwide.
• Contagious, caused by primary pathogens.
• Acquired from infected persons, pets (cats or dogs), and livestock animals (goats, sheep, camel, cows, horses).

Diagnosis

• Diagnosis of dermatophyte infection can based on clinical picture, Wood's light, direct examination, and culture.

Treatment

• Systemic agents (oral) such as Griseofulvin (drug of choice), Itraconazole, Allylamine, and Ketoconazole.
• Topical agents such as white field, clotrimazole, and miconazole.
• Prophylaxis against Tinea pedis includes keeping the feet dry and rubbing between toes with dry gauze and alcohol.