B40.1
BillableChronic pulmonary blastomycosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B40.1 an HCC code?
Yes. B40.1 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess under the V24 model but is not retained in V28.
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for B40.1
For B40.1to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed B40.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B40.1 is the ICD-10-CM diagnosis code for chronic pulmonary blastomycosis. A long-standing fungal lung infection caused by Blastomyces that develops gradually with persistent cough, chest pain, and progressive respiratory symptoms. B40.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering mycoses (b35-b49).
Under the older CMS-HCC V24 model, B40.1 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess (HCC 115) with a community, non-dual, aged base RAF weight of 0.339. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Chronic form often mimics tuberculosis or lung cancer; review imaging findings and clinical course carefully. Because B40.1 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B40.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Chronic form often mimics tuberculosis or lung cancer; review imaging findings and clinical course carefully
- •Ensure documentation clearly indicates chronic progression over weeks to months
Clinical Significance
Chronic pulmonary blastomycosis presents as a progressive fibrocavitary lung disease that mimics tuberculosis and lung cancer. Long-term antifungal therapy is typically required, and the chronic nature indicates ongoing disease burden and resource utilization that risk adjustment models need to capture accurately.
Documentation Requirements
- ✓Documented chronic/progressive course over weeks to months
- ✓Imaging showing mass lesions, fibronodular disease, or cavitary changes
- ✓Positive Blastomyces culture, antigen, or histopathology from respiratory specimens
- ✓Exclusion of tuberculosis and malignancy documented in the record
- ✓Ongoing antifungal treatment plan documented
Commonly Confused Codes
- •B40.0 (Acute pulmonary blastomycosis) - acute form has rapid onset with pneumonic infiltrates; chronic shows progressive fibrocavitary disease
- •A15.0 (Tuberculosis of lung) - blastomycosis can be radiographically identical to TB; microbiologic studies differentiate
- •C34.90 (Malignant neoplasm of unspecified part of bronchus or lung) - mass-like blastomycosis can be confused with lung cancer until biopsy confirms fungal etiology