ICD-10 B59
Billable / Specific HCC v28: 6 MCCPneumocystosis
About ICD-10-CM B59
ICD-10-CM code B59 represents Pneumocystosis. This is a billable/specific code in the Infectious and Parasitic Diseases chapter (block B59). The 2026 edition of ICD-10-CM B59 became effective on October 1, 2025.
Coding Tips for B59
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
B59 is a CMS-HCC v28 risk-adjustment code (category 6). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
B59 is designated MCC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-MCC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag MCC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under B59. Per CMS ICD-10-CM Tabular 2026.
- Pneumonia due to Pneumocystis carinii
- Pneumonia due to Pneumocystis jirovecii
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, MCC
codes Pneumocystosis. As a Major Complication/Comorbidity (MCC), this can shift the DRG assignment to a higher-weighted category, substantial reimbursement impact.
Medicare LCD Coverage for B59
Local Coverage Determinations (LCDs) from CMS MACs that list B59 as a covered diagnosis.
Showing top 10 of 742 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing B59.
1 Aetna
1 Cigna
5 Medicare
CPT Codes Commonly Billed with B59
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 94726 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94004 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94621 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94011 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94003 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94668 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94070 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94664 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 94012 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
- 31502 CMS LCD: Billing and Coding: Respiratory Therapy (Respiratory Care) CMS LCD
Convert B59 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| B59 | 1363 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To B59
Other codes in section B50-B64 (Protozoal diseases).
ICD-10 B59, Billing FAQ
Is ICD-10 code B59 billable? +
Yes, B59 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to B59? +
ICD-10 B59 includes: Pneumonia due to Pneumocystis carinii; Pneumonia due to Pneumocystis jirovecii.
Does B59 affect Medicare Advantage HCC risk adjustment? +
Yes. B59 maps to CMS-HCC v28 category 6. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is B59 a CC or MCC for inpatient DRG? +
Yes, this code is designated as MCC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with B59? +
Procedures frequently paired with B59 include: 94726, 94004, 94621, 94011, 94003.
What ICD-9 codes does B59 map to? +
Per CMS GEMs, B59 maps to ICD-9 codes: 1363. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on June 1, 2026.
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