B36.3 Black piedra

Name of the Condition

• Black piedra

Summary

Black piedra is a superficial fungal infection that forms hard, dark nodules on hair shafts. It primarily affects the scalp, beard, or body hair and is caused by the fungus Piedraia hortae. The condition is generally mild and cosmetic, though it may cause hair breakage or discomfort. It is more common in tropical and subtropical regions.

Causes

Black piedra is caused by the fungus Piedraia hortae, which thrives in warm, humid environments. Infection occurs through direct contact with contaminated hair, soil, or objects. The fungus colonizes the hair shaft, forming hard, pigmented nodules that adhere to the hair.

Risk Factors

• Warm, humid climates
• Poor hair hygiene or infrequent washing
• Occupational or recreational exposure to soil or contaminated surfaces
• Crowded living conditions
• Weakened immune system (rare)

Symptoms

• Hard, dark brown to black nodules on hair shafts
• Nodules may be smooth or rough in texture
• Hair breakage or brittleness
• Mild itching or irritation (occasionally)

Diagnosis

Diagnosis is based on clinical evaluation of the affected hair. Microscopic examination of hair samples reveals the characteristic dark, pigmented nodules and fungal elements. Culturing the fungus may confirm the causative organism, though this is not always necessary for diagnosis.

Treatment Options

• Shaving or cutting affected hair (effective for localized cases)
• Topical antifungal agents (e.g., selenium sulfide, ketoconazole)
• Oral antifungal medications (for severe or widespread cases)
• Improved hair hygiene and regular washing

Prognosis and Follow-Up

Prognosis is excellent with appropriate treatment. Nodules typically resolve within weeks to months after starting therapy. Recurrence is possible if exposure to the fungus continues. Follow-up may be recommended to monitor for recurrence or complications.

Complications

• Hair breakage or temporary hair loss
• Secondary bacterial infection (rare)
• Cosmetic concerns or psychological distress

Lifestyle & Prevention

• Maintain good hair hygiene with regular washing
• Avoid sharing personal items like combs or brushes
• Limit exposure to contaminated soil or surfaces in tropical regions
• Keep hair dry and well-ventilated to reduce fungal growth

When to Seek Professional Help

Seek medical attention if:

• Nodules persist or worsen despite home care
• Hair loss or breakage is significant
• Signs of secondary infection (e.g., redness, pus) develop
• The condition causes discomfort or distress

Tips for Medical Coders

Use code B36.3 for black piedra. Documentation should specify the affected body area (e.g., scalp, beard) and confirm the presence of characteristic dark nodules on hair shafts. Include details of clinical evaluation, microscopic findings, or treatment to support coding accuracy.