What is ICD-10 code B39.1?

B39.1 is the ICD-10-CM diagnosis code for Chronic pulmonary histoplasmosis capsulati. A long-standing fungal lung infection caused by Histoplasma capsulatum that develops slowly over months or years with persistent respiratory symptoms. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). B39.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. B39.1 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. B39.1 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. B39.1 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for B39.1?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. B39.1 was a payment HCC under V24 (Pneumococcal Pneumonia, Empyema, Lung Abscess) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting B39.1?

Chronic form often mimics tuberculosis or other chronic lung diseases; review imaging and clinical course Ensure documentation clearly indicates chronic progression rather than acute presentation Because B39.1 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

B39.1: Chronic pulmonary histoplasmosis capsulati — ICD-10 | Pneumococcal Pneumonia, Empyema, Lung

ICD-10-CM Code View

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Code lookupB39.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Mycoses (B35-B49)

B39.1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Chronic pulmonary histoplasmosis capsulati

A long-standing fungal lung infection caused by Histoplasma capsulatum that develops slowly over months or years with persistent respiratory symptoms.

Buddy Insight

Chronic pulmonary histoplasmosis capsulati is a progressive cavitary lung disease that closely mimics pulmonary tuberculosis.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Mapped

HCC 115

Pneumococcal Pneumonia, Empye...

RAF 0.339

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 115

Pneumococcal Pneumonia, Empye...

RAF 0.0

RXHCC

Not risk-adjusted for this model/period.

RAF 0

Code Trumping

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Code Book Path

Official

B39Histoplasmosis

B39.1Chronic pulmonary histoplasmosis capsulati

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for B39.1 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B39.1 in this effective period.

Related Child Codes

Official

B39.0Acute pulmonary histoplasmosis capsulati

B39.2Pulmonary histoplasmosis capsulati, unspecified

B39.3Disseminated histoplasmosis capsulati

B39.4Histoplasmosis capsulati, unspecified

B39.5Histoplasmosis duboisii

Includes

Official

ICD-10-CM does not list Includes notes for B39.1 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B39.1 in this effective period.

Code First

Official

associated AIDS (B20)

Use Additional

Official

code for any associated manifestations, such as:
endocarditis (I39)
meningitis (G02)
pericarditis (I32)
retinitis (H32)

Code Also

Official

ICD-10-CM does not list Code Also instructions for B39.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of chronic/progressive course (months to years)

Imaging showing upper lobe cavitary disease, progressive fibrosis, or bullae

Positive Histoplasma culture, antigen, or complement fixation titers

Underlying lung disease documented (emphysema, chronic obstructive pulmonary disease)

MEAT Support

HCC Buddy guidance

Documentation of chronic/progressive course (months to years)

Imaging showing upper lobe cavitary disease, progressive fibrosis, or bullae

Positive Histoplasma culture, antigen, or complement fixation titers

Underlying lung disease documented (emphysema, chronic obstructive pulmonary disease)

Audit Caution

HCC Buddy guidance

Miscoding as tuberculosis due to similar radiographic appearance — culture and serologic testing distinguish the two

Using the unspecified pulmonary code (B39.2) when documentation supports chronic progressive disease

Failing to also code the underlying emphysema or chronic obstructive pulmonary disease that predisposes to this condition

Common Mistakes

HCC Buddy guidance

B39.0 (Acute pulmonary histoplasmosis capsulati) - acute form has rapid onset; chronic shows progressive cavitary disease

A15.0 (Tuberculosis of lung) - chronic histoplasmosis mimics TB; microbiologic confirmation differentiates

B39.4 (Histoplasmosis capsulati, unspecified) - avoid when pulmonary site and chronicity are documented

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is B39.1 an HCC code?

Yes. B39.1 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess under the V24 model but is not retained in V28.

HCC Category Mapping

V24HCC 115, Pneumococcal Pneumonia, Empyema, Lung Abscess

0.339

ESRDHCC 115, Pneumococcal Pneumonia, Empyema, Lung Abscess

0.000

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 B39.1

For B39.1to 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 B39.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B39.1 is the ICD-10-CM diagnosis code for chronic pulmonary histoplasmosis capsulati. A long-standing fungal lung infection caused by Histoplasma capsulatum that develops slowly over months or years with persistent respiratory symptoms. B39.1 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, B39.1 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 other chronic lung diseases; review imaging and clinical course. Because B39.1 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 B39.1 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 other chronic lung diseases; review imaging and clinical course
•Ensure documentation clearly indicates chronic progression rather than acute presentation

Clinical Significance

Chronic pulmonary histoplasmosis capsulati is a progressive cavitary lung disease that closely mimics pulmonary tuberculosis. It typically affects patients with underlying structural lung disease such as emphysema. Accurate differentiation from TB and other chronic lung conditions is critical for appropriate treatment and risk coding.

Documentation Requirements

✓Documentation of chronic/progressive course (months to years)
✓Imaging showing upper lobe cavitary disease, progressive fibrosis, or bullae
✓Positive Histoplasma culture, antigen, or complement fixation titers
✓Underlying lung disease documented (emphysema, chronic obstructive pulmonary disease)
✓Evidence that tuberculosis has been ruled out (negative acid-fast bacilli cultures)

Commonly Confused Codes

•B39.0 (Acute pulmonary histoplasmosis capsulati) - acute form has rapid onset; chronic shows progressive cavitary disease
•A15.0 (Tuberculosis of lung) - chronic histoplasmosis mimics TB; microbiologic confirmation differentiates
•B39.4 (Histoplasmosis capsulati, unspecified) - avoid when pulmonary site and chronicity are documented