Tinea nigra

File:Hortaea-werneckii-fungus

Hortaea-werneckii-fungus

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 macules, typically appearing on the palms and soles. It is a relatively rare infection and is more commonly found in tropical and subtropical regions.

Presentation

The primary symptom of tinea nigra is the appearance of darkly pigmented 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 size. They are most commonly found on the palms of the hands and the soles of the feet, but can occasionally appear on other parts of the body.

Cause

Tinea nigra is caused by the fungus Hortaea werneckii. This organism is a type of dematiaceous fungi, which are known for their dark pigmentation. The fungus is typically found in soil, decaying vegetation, and wood, particularly in warm, humid environments. Infection occurs when the fungus comes into contact with the skin, often through minor cuts or abrasions.

Diagnosis

Diagnosis of tinea nigra is primarily clinical, based on the characteristic appearance of the lesions. However, confirmation can be achieved through microscopic examination and culture of skin scrapings. Under the microscope, the fungus appears as darkly pigmented, septate hyphae and yeast-like cells. Potassium hydroxide (KOH) preparation is commonly used to visualize the fungal elements.

Treatment

Treatment of tinea nigra typically involves the use of topical antifungal agents. Commonly used medications include miconazole, clotrimazole, and terbinafine. These treatments are usually effective, and the infection often resolves within a few weeks. In some cases, keratolytic agents such as salicylic acid may be used to help remove the pigmented layer of skin.

Prevention

Preventing tinea nigra involves minimizing exposure to the fungus. This can be achieved by maintaining good personal hygiene, avoiding walking barefoot in areas where the fungus is likely to be present, and promptly treating any minor skin injuries.

Epidemiology

Tinea nigra is more commonly found in tropical and subtropical regions, including parts of Central America, South America, Africa, and Asia. It affects individuals of all ages but is more frequently seen in children and young adults. The condition is not contagious and does not spread from person to person.

See also

• Dermatophytosis
• Pityriasis versicolor
• Fungal skin infections

External links

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