B58.3 ICD-10-CM Code: Pulmonary toxoplasmosis
B58.3 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 · free HCC coding tools
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Protozoal diseases (B50-B64)
B58.3
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidancePulmonary 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.
Buddy Insight
Pulmonary toxoplasmosis is a serious opportunistic lung infection in severely immunocompromised patients, particularly those with AIDS and CD4 counts below 100.
CMS-HCC V28
MappedHCC 6
Coefficient HCC 6: 0.381 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 006
Code-level coefficient reference
ESRD/PACE
MappedHCC 6
Code-level coefficient reference
RXHCC
MappedHCC 5
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for B58.3. 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
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
OfficialNo Code First sequencing instructions are included in this display for B58.3. 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
OfficialNo Code Also instructions are included in this display for B58.3. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 B58.3 an HCC code?
Yes. B58.3 (Pulmonary toxoplasmosis) 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: B58.3 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
- B58.3
- Description
- Pulmonary toxoplasmosis
- HCC (V28)
- HCC 6 — Opportunistic Infections
- RAF reference coefficient
- 0.381
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
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 B58.3 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for B58.3
For B58.3, 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
B58.3 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 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.
This code is typically used in immunocompromised patients; consider coding the underlying condition (such as HIV/AIDS) as an additional diagnosis code. For B58.3, 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 B58.3 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