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ICD-10-CM 2027

ICD-10 code for Pneumocystosis

B59

Pneumocystosis

From the official ICD-10-CM alphabetic index entry “Pneumocystosis (with pneumonia)”. Page updated September 29, 2026.

About coding Pneumocystosis

The ICD-10-CM code for Pneumocystosis is B59 (Pneumocystosis).

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 177 (Respiratory Infections and Inflammations with MCC, relative weight 1.6092), DRG 178 (Respiratory Infections and Inflammations with CC, relative weight 0.9744), DRG 179 (Respiratory Infections and Inflammations without CC/MCC, relative weight 0.7345), DRG 791 (Prematurity with Major Problems, relative weight 4.1075), DRG 793 (Full Term Neonate with Major Problems, relative weight 4.2195), DRG 974 (HIV with Major Related Condition with MCC, relative weight 3.0506) and 2 more, in MDC 04 (Diseases and Disorders of the Respiratory System), MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period) and MDC 25 (Human Immunodeficiency Virus Infections), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Common questions about Pneumocystosis ICD-10 codes

What is the ICD-10 code for Pneumocystosis?

B59 — Pneumocystosis.

Is B59 billable?

Yes. B59 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can B59 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict B59 as a principal diagnosis.

Is B59 a CC or MCC?

B59 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.