B36.1 Tinea nigra

Name of the Condition

• Tinea nigra

Summary

Tinea nigra is a superficial fungal infection that causes dark, non-scaly patches on the skin, typically affecting the palms of the hands or soles of the feet. It is caused by the fungus Hortaea werneckii and is generally mild, with cosmetic concerns being the primary issue. The condition is more common in tropical or subtropical regions.

Causes

Tinea nigra is caused by the fungus Hortaea werneckii, which thrives in warm, humid environments. Infection occurs through direct contact with contaminated surfaces, soil, or objects, as the fungus is found in these settings. The fungus penetrates the outermost layer of the skin, leading to the characteristic discoloration.

Risk Factors

• Warm, humid climates
• Prolonged exposure to moist environments
• Occupational or recreational activities involving soil or contaminated surfaces
• Weakened immune system (rare)

Symptoms

• Dark brown to black, non-scaly patches on the skin
• Patches typically appear on the palms or soles
• No significant itching or discomfort
• Patches may be flat or slightly raised

Diagnosis

Diagnosis is based on clinical evaluation of the affected area, often confirmed by microscopic examination of skin scrapings. The presence of pigmented, branching hyphae under a microscope is diagnostic. Culturing the fungus may be used for confirmation in some cases.

Treatment Options

• Topical antifungal agents (e.g., Whitfield's ointment, imidazoles)
• Scraping or light abrasion of the affected area to remove pigmented skin
• Oral antifungals are rarely needed unless the infection is widespread or resistant

Prognosis and Follow-Up

With appropriate treatment, tinea nigra typically resolves within weeks to months. Recurrence is uncommon but may occur if exposure to the fungus continues. Follow-up is generally not required unless symptoms persist or worsen.

Complications

• Cosmetic concerns due to persistent discoloration
• Rare secondary bacterial infection if the area is scratched or irritated

Lifestyle & Prevention

• Avoid contact with contaminated soil or surfaces in tropical regions
• Keep hands and feet dry, especially after exposure to moisture
• Practice good hygiene, including regular handwashing

When to Seek Professional Help

Seek medical attention if the dark patches spread, change in appearance, or cause discomfort. A healthcare provider can confirm the diagnosis and recommend appropriate treatment.

Tips for Medical Coders

When coding for tinea nigra, use ICD-10-CM code B36.1. Ensure documentation includes the affected body part (e.g., palms, soles) and any relevant clinical findings to support the diagnosis. Note that this code is specific to tinea nigra and should not be used for other superficial mycoses.