B58.2 maps to CMS-HCC V28 6. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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Code lookupB58.2

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Protozoal diseases (B50-B64)

B58.2

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

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.

Buddy Insight

Toxoplasma meningoencephalitis is one of the most common central nervous system opportunistic infections in AIDS patients, typically occurring when CD4 counts fall below 100.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 6

Opportunistic Infections

Coefficient HCC 6: 0.381 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 006

HHS-HCC 006 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 6

Opportunistic Infections

Code-level coefficient reference

RXHCC

Mapped

HCC 5

Opportunistic Infections

Code-level coefficient reference

Code Book Path

Official

B58Toxoplasmosis B58.2Toxoplasma meningoencephalitis

Inclusion Terms

Official

No inclusion terms are included in this display for B58.2. Check the code and parent instructions in the Code Book.

Excludes 2

Official

carrier or suspected carrier of infectious disease (Z22.-)Inherited from A00-B99
infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)Inherited from A00-B99
infectious and parasitic diseases specific to the perinatal period (P35-P39)Inherited from A00-B99
influenza and other acute respiratory infections (J00-J22)Inherited from A00-B99

Related Codes

Official

B58.0Toxoplasma oculopathy B58.1Toxoplasma hepatitis B58.3Pulmonary toxoplasmosis B58.8Toxoplasmosis with other organ involvement B58.9Toxoplasmosis, unspecified

Includes

Official

diseases generally recognized as communicable or transmissibleInherited from A00-B99, B58
infection due to Toxoplasma gondiiInherited from A00-B99, B58

Excludes 1

Official

certain localized infections - see body system-related chaptersInherited from A00-B99, B50-B64, B58
amebiasis (A06.-)Inherited from A00-B99, B50-B64, B58
other protozoal intestinal diseases (A07.-)Inherited from A00-B99, B50-B64, B58
congenital toxoplasmosis (P37.1)Inherited from A00-B99, B50-B64, B58

Code First

Official

No Code First sequencing instructions are included in this display for B58.2. Check the code and parent instructions in the Code Book.

Use Additional

Official

code to identify resistance to antimicrobial drugs (Z16.-)Inherited from A00-B99

Code Also

Official

No Code Also instructions are included in this display for B58.2. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

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

MEAT Support

HCC Buddy guidance

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

Audit Caution

HCC Buddy guidance

Confusing Toxoplasma encephalitis with primary central nervous system lymphoma — both cause ring-enhancing lesions in AIDS patients; empiric Toxoplasma treatment response differentiates

Not coding HIV disease (B20) as the underlying condition enabling this opportunistic infection

Using unspecified toxoplasmosis (B58.9) when central nervous system involvement is clearly documented on imaging

Failing to document the specific neurologic manifestations (seizures, hemiparesis) that may require additional codes

Common Mistakes

HCC Buddy guidance

B58.1 (Toxoplasma hepatitis) - hepatic involvement, not central nervous system

B58.3 (Pulmonary toxoplasmosis) - lung involvement, not brain

A87.9 (Viral meningitis, unspecified) - must distinguish toxoplasma from viral or other infectious causes via imaging and serology

C71.9 (Malignant neoplasm of brain, unspecified) - primary CNS lymphoma is the main differential for ring-enhancing lesions in AIDS

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is B58.2 an HCC code?

Yes. B58.2 (Toxoplasma meningoencephalitis) maps to HCC 6, Opportunistic Infections under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.381. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: B58.2 is billable and maps to V28 HCC 6, Opportunistic Infections. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: B58.2
Description: Toxoplasma meningoencephalitis
HCC (V28): HCC 6 — Opportunistic Infections
RAF reference coefficient: 0.381
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 6, Opportunistic Infections

0.381

ESRDHCC 6, Opportunistic Infections

Not separately weighted

RxHCCHCC 5, Opportunistic Infections

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work B58.2 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for B58.2

For B58.2, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

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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 source-labeled community, non-dual, aged reference coefficient of 0.381. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Always verify the patient has confirmed toxoplasmosis with meningoencephalitis involvement before coding this diagnosis; imaging or CSF analysis findings should support the diagnosis. For B58.2, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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

Commonly Confused Codes

•B58.1 (Toxoplasma hepatitis) - hepatic involvement, not central nervous system
•B58.3 (Pulmonary toxoplasmosis) - lung involvement, not brain
•A87.9 (Viral meningitis, unspecified) - must distinguish toxoplasma from viral or other infectious causes via imaging and serology
•C71.9 (Malignant neoplasm of brain, unspecified) - primary CNS lymphoma is the main differential for ring-enhancing lesions in AIDS