Tinea nigra

Tinea nigra new image

Tinea nigra is a superficial fungal infection of the skin caused by the dematiaceous (darkly pigmented) fungus Hortaea werneckii. This condition is characterized by brown to black, non-scaly patches on the palms of the hands and the soles of the feet. It is a relatively rare infection and is most commonly found in tropical and subtropical regions.

Presentation

The primary symptom of tinea nigra is the appearance of dark patches on the skin. These patches are usually asymptomatic, meaning they do not cause pain or itching. The lesions are typically well-defined, flat, and can vary in color from light brown to black. They are most commonly found on the palms and soles but can occasionally appear on other parts of the body.

Pathogenesis

Tinea nigra is caused by the fungus Hortaea werneckii, which is a type of dematiaceous fungi. The fungus produces melanin, which gives the lesions their characteristic dark color. The infection is usually acquired through direct contact with contaminated soil, wood, or decaying vegetation. The fungus thrives in warm, humid environments, which is why the infection is more prevalent in tropical and subtropical regions.

Diagnosis

Diagnosis of tinea nigra is typically made through clinical examination and confirmed by laboratory tests. A skin scraping from the affected area can be examined under a microscope after being treated with potassium hydroxide (KOH). The presence of darkly pigmented, septate hyphae and yeast-like cells is indicative of Hortaea werneckii. Culture and histopathological examination can also be used to confirm the diagnosis.

Treatment

Treatment for tinea nigra is usually straightforward and involves the use of topical antifungal agents. Commonly used medications include miconazole, clotrimazole, and terbinafine. These treatments are typically applied to the affected area once or twice daily for several weeks. In some cases, keratolytic agents such as salicylic acid may be used to help remove the outer layer of skin and enhance the effectiveness of the antifungal treatment.

Prevention

Preventing tinea nigra involves minimizing exposure to the environmental sources of the fungus. This includes avoiding direct contact with contaminated soil, wood, and vegetation, especially in tropical and subtropical regions. Maintaining good personal hygiene and keeping the skin dry can also help reduce the risk of infection.

Related Pages

• Dermatophyte
• Fungal infection
• Antifungal medication
• Superficial mycoses
• Hortaea werneckii