ICD-10 Code B40.9 – Blastomycosis, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B40.9 – Blastomycosis, unspecified
What it is
B40.9 identifies blastomycosis when the record does not specify the site or type of infection. It is a fungal infection caused by Blastomyces, and you should use the unspecified code only when documentation is limited.
Clinical signs
Clinical features vary; refer to documentation. Blastomycosis may present with pulmonary symptoms or spread beyond the lungs, but the chart must support the diagnosis and not specify a more detailed form.
When to use this code
Use B40.9 when the provider documents blastomycosis without naming pulmonary, cutaneous, or disseminated disease. It also fits when the note confirms blastomycosis but lacks enough detail for a more specific code. Check documentation before assigning an unspecified code.
Do not use for
Do not use B40.9 if the record identifies a more specific blastomycosis type or another fungal infection. Do not code suspected exposure or ruled-out disease as confirmed blastomycosis.
Coding tip
If the note says only “blastomycosis,” B40.9 is appropriate; otherwise, code the documented site or manifestation.