B58.2
BillableToxoplasma meningoencephalitis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B58.2 an HCC code?
Yes. B58.2 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 B58.2
For B58.2 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 B58.2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B58.2 is the ICD-10-CM diagnosis code for toxoplasma meningoencephalitis. This is a serious brain infection caused by the Toxoplasma parasite that affects the protective membranes surrounding the brain and spinal cord. It typically occurs in people with weakened immune systems, such as those with HIV/AIDS. B58.2 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, B58.2 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.439. Under the older V24 model, B58.2 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.
Always verify the patient has confirmed toxoplasmosis with meningoencephalitis involvement before coding this diagnosis; imaging or CSF analysis findings should support the diagnosis. Because B58.2 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 B58.2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always verify the patient has confirmed toxoplasmosis with meningoencephalitis involvement before coding this diagnosis; imaging or CSF analysis findings should support the diagnosis
- •This code should be paired with the underlying immunocompromised condition (such as B20 for HIV) when applicable, as toxoplasma meningoencephalitis is an opportunistic infection
Clinical Significance
Toxoplasma meningoencephalitis is one of the most common central nervous system opportunistic infections in AIDS patients, typically occurring when CD4 counts fall below 100. It presents with ring-enhancing brain lesions on imaging and is a medical emergency requiring immediate empiric treatment. It is a key AIDS-defining illness that significantly impacts patient acuity and resource utilization.
Documentation Requirements
- ✓Brain MRI or CT showing ring-enhancing lesions, typically in the basal ganglia
- ✓Positive Toxoplasma IgG serology (nearly always positive in reactivation disease)
- ✓CD4 count documented (typically <100 cells/microL)
- ✓Neurologic symptoms: headache, confusion, seizures, focal deficits, altered consciousness
- ✓Clinical response to empiric anti-Toxoplasma therapy (pyrimethamine + sulfadiazine)
- ✓HIV disease status documented