B40.3 Cutaneous blastomycosis

Name of the Condition

• Cutaneous blastomycosis

Summary

Cutaneous blastomycosis is a fungal infection of the skin caused by Blastomyces dermatitidis (and related species). It typically occurs as a result of hematogenous dissemination from a primary pulmonary infection, though direct inoculation through skin wounds is rare. The condition presents with skin lesions and may indicate systemic involvement, particularly in immunocompromised individuals.

Causes

The infection is caused by Blastomyces fungi, which are found in soil and decaying organic matter in endemic regions. Spores inhaled into the lungs convert to yeast, multiply, and may spread to the skin via the bloodstream. Direct skin inoculation is uncommon but possible through wounds exposed to contaminated material.

Risk Factors

• Residence in or travel to endemic areas (e.g., parts of North America, particularly the Ohio and Mississippi River valleys).
• Occupational or recreational exposure to soil (e.g., construction, forestry, gardening).
• Immunocompromised states (e.g., HIV/AIDS, organ transplantation, chronic steroid use).
• Male gender (higher incidence reported).
• Advanced age.

Symptoms

• Skin lesions: Painless or painful papules, nodules, or ulcers that may ulcerate or crust, often resembling other skin conditions (e.g., squamous cell carcinoma, pyoderma gangrenosum).
• Lesions may appear on any body part, including the face, extremities, or trunk.
• Systemic symptoms (e.g., fever, weight loss) may accompany disseminated disease.

Diagnosis

Diagnosis involves clinical evaluation of skin lesions, supported by laboratory tests. Direct microscopy or culture of lesion samples (e.g., biopsy, exudate) may identify Blastomyces yeast. Histopathology showing broad-based budding yeast confirms the diagnosis. Pulmonary or systemic involvement may be assessed via imaging or additional testing if suspected.

Treatment Options

Treatment typically involves antifungal medications, such as itraconazole for mild to moderate cases or amphotericin B for severe or disseminated disease. Duration depends on disease severity and response. Immunocompromised patients may require longer therapy. Surgical debridement of lesions is rarely needed.

Prognosis and Follow-Up

Prognosis is generally good with appropriate antifungal treatment, though immunocompromised individuals may have a higher risk of recurrence or complications. Follow-up includes monitoring for treatment response and resolution of lesions. Repeat testing may be performed if symptoms persist or recur.

Complications

• Disseminated infection (e.g., to lungs, bones, central nervous system) if left untreated.
• Chronic skin ulcers or scarring.
• Increased risk of severe disease in immunocompromised patients.

Lifestyle & Prevention

• Avoid exposure to soil or decaying organic matter in endemic areas, especially during activities like gardening or construction.
• Wear protective clothing (e.g., gloves, masks) when handling potentially contaminated material.
• Seek prompt medical evaluation for unexplained skin lesions, particularly after travel to endemic regions.

When to Seek Professional Help

Consult a healthcare provider for persistent, unexplained skin lesions, especially if accompanied by systemic symptoms (e.g., fever, weight loss) or if you have risk factors for blastomycosis. Early diagnosis and treatment improve outcomes.

Tips for Medical Coders

Use code B40.3 for cutaneous blastomycosis. Document the presence of skin lesions and any associated systemic involvement to support coding. Ensure clinical correlation with laboratory or histopathological confirmation of Blastomyces infection when available.