B40.7 Disseminated blastomycosis

Name of the Condition

• Disseminated blastomycosis

Summary

Disseminated blastomycosis is a systemic fungal infection caused by Blastomyces dermatitidis (and related species) that occurs when the infection spreads beyond the lungs to other body sites. It typically arises from an initial pulmonary infection and can involve multiple organs, including the skin, bones, central nervous system, or genitourinary tract. The condition may present with varied clinical manifestations, ranging from mild to severe, and is more common in immunocompromised individuals.

Causes

The infection originates from inhaling airborne spores of Blastomyces fungi, which are found in soil and decaying organic matter in endemic regions. After inhalation, the spores convert to yeast in the lungs, where they multiply and may disseminate hematogenously to other organs. Direct inoculation through skin wounds is rare.

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

• Pulmonary: Cough (productive or non-productive), chest pain, dyspnea, fever, night sweats, weight loss.
• Systemic: Fatigue, myalgia, arthralgia.
• Disseminated disease may involve skin (e.g., nodules, ulcers), bones (e.g., osteomyelitis), central nervous system (e.g., meningitis), or genitourinary tract (e.g., prostatitis).

Diagnosis

Diagnosis involves a combination of clinical evaluation, imaging, and laboratory testing. Chest radiography or CT may show pulmonary infiltrates or nodules. Microbiological confirmation is achieved by identifying Blastomyces yeast in tissue samples (e.g., biopsy, sputum, or body fluids) via culture, histopathology, or antigen testing. Serologic tests may support diagnosis but are less specific.

Treatment Options

Treatment typically includes antifungal therapy, with the choice of agent and duration depending on disease severity and patient factors. Itraconazole is often used for mild to moderate cases, while amphotericin B is preferred for severe or disseminated disease. Adjunctive therapies or surgical intervention may be necessary for complications (e.g., abscess drainage).

Prognosis and Follow-Up

Prognosis varies based on disease extent, host immunity, and timely treatment. Most patients respond to therapy, but severe or untreated cases can be fatal. Follow-up includes monitoring for treatment response, symptom resolution, and potential relapse, with repeat imaging or laboratory testing as clinically indicated.

Complications

• Respiratory failure or chronic lung disease.
• Disseminated infection involving skin, bones, or central nervous system.
• Meningitis or other neurologic sequelae.
• Organ dysfunction (e.g., renal, hepatic) in severe cases.

Lifestyle & Prevention

• Avoid exposure to soil or decaying organic matter in endemic areas, especially during activities like gardening or construction.
• Wear protective masks or clothing when working in high-risk environments.
• Promptly treat underlying immunocompromising conditions to reduce infection risk.

When to Seek Professional Help

Seek medical attention if you experience persistent respiratory symptoms (e.g., cough, fever, chest pain), unexplained weight loss, or skin lesions, particularly if you live in or have traveled to an endemic region or have a weakened immune system.

Tips for Medical Coders

Use code B40.7 for documented disseminated blastomycosis. Ensure clinical documentation specifies systemic involvement (e.g., skin, bones, CNS) to support the code. Verify that the diagnosis aligns with the ICD-10-CM coding guidelines for fungal infections and disseminated disease.