ICD-10 Code B40.3 – Cutaneous blastomycosis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B40.3 – Cutaneous blastomycosis
What it is
B40.3 identifies blastomycosis involving the skin. Use this code when Blastomyces infection is documented as cutaneous, whether primary skin disease or spread from another site.
Clinical signs
Typical findings include verrucous, ulcerative, or crusted skin lesions that may enlarge slowly. Clinical features vary; refer to documentation and confirm that the infection is specifically described as cutaneous.
When to use this code
Use B40.3 when the provider documents cutaneous blastomycosis, skin blastomycosis, or blastomycotic skin lesions. Code it when the record clearly links the fungal infection to the skin, even if other sites are also involved. Check documentation if the site is not explicit.
Do not use for
Do not use this code for nonspecific fungal dermatitis, other mycoses, or suspected blastomycosis without confirmation. If the infection site is listed elsewhere or not stated, check documentation.
Coding tip
Verify the organism and the anatomic site; B40.3 requires both blastomycosis and skin involvement to be documented.