B58.3
BillablePulmonary toxoplasmosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B58.3 an HCC code?
Yes. B58.3 maps to Opportunistic Infections under the CMS-HCC V28 risk adjustment model (and Opportunistic Infections under V24).
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 B58.3
For B58.3 to 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 B58.3 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B58.3 is the ICD-10-CM diagnosis code for pulmonary toxoplasmosis. This is a lung infection caused by the parasite Toxoplasma gondii, which can occur in people with weakened immune systems, particularly those with HIV/AIDS. The infection affects the lungs and can cause respiratory symptoms like cough and difficulty breathing. B58.3 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering protozoal diseases (b50-b64).
Under the CMS-HCC V28 risk adjustment model, B58.3 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.439. Under the older V24 model, B58.3 mapped to the same category but with a base RAF weight of 0.440 — V28 recalibrated weights across the entire model. 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.
This code is typically used in immunocompromised patients; consider coding the underlying condition (such as HIV/AIDS) as an additional diagnosis code. Because B58.3 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 B58.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code is typically used in immunocompromised patients; consider coding the underlying condition (such as HIV/AIDS) as an additional diagnosis code
- •Verify documentation specifies pulmonary involvement rather than other forms of toxoplasmosis (such as cerebral or ocular) to ensure accurate code selection
Clinical Significance
Pulmonary toxoplasmosis is a serious opportunistic lung infection in severely immunocompromised patients, particularly those with AIDS and CD4 counts below 100. It can present as rapidly progressive pneumonia mimicking Pneumocystis pneumonia, and carries high mortality if not recognized and treated promptly. It is much less common than central nervous system toxoplasmosis but equally life-threatening.
Documentation Requirements
- ✓Bronchoalveolar lavage or lung biopsy confirming Toxoplasma gondii
- ✓Chest imaging showing diffuse interstitial or alveolar infiltrates
- ✓CD4 count and HIV viral load documented
- ✓Respiratory symptoms: nonproductive cough, dyspnea, fever
- ✓Negative Pneumocystis testing to differentiate from Pneumocystis pneumonia
- ✓Treatment with pyrimethamine + sulfadiazine documented
Commonly Confused Codes
- •B59 (Pneumocystosis) - most common diagnostic confusion; both cause diffuse pneumonia in AIDS; bronchoalveolar lavage differentiates
- •B58.2 (Toxoplasma meningoencephalitis) - central nervous system involvement, not pulmonary; check for concurrent disease
- •B58.9 (Toxoplasmosis, unspecified) - do not use when pulmonary site is confirmed