Pneumocystosis
In Protozoal diseases (B50-B64), chapter 1: Certain Infectious and Parasitic Diseases
- B59 is billable and valid on claims for FY 2027. If the record has more detail, check the other codes under B50-B64 below.
- As a secondary diagnosis it is an MCC (major complication), which can raise the MS-DRG payment. It doesn't count when the principal diagnosis is one of 105 closely related codes.
- Counts toward HCC 6 (Opportunistic Infections) in the Medicare Advantage risk model (CMS-HCC V28).
- AHRQ's Chronic Condition Indicator classes it as not chronic (an acute or short-term condition).
- 280 US deaths in 2024 had an underlying cause in category B59, per the National Vital Statistics System on CDC WONDER. Death records use WHO ICD-10, so the count is for the whole category.
Also indexed as: Disease, protozoal, pneumocystosis; Infection, Pneumocystis carinii; Infection, Pneumocystis jirovecii; Pneumocystis carinii pneumonia; Pneumocystis jirovecii; Pneumocystosis; Pneumonia, in, pneumocystosis; Pneumonia, interstitial, plasma cell; Pneumonia, plasma cell; Pneumonia, Pneumocystis
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Instructional notes
Includes: conditions that are coded here
- Pneumonia due to Pneumocystis carinii
- Pneumonia due to Pneumocystis jirovecii
Official coding guidelines
From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.
Rules for coding infections and parasitic diseases, including HIV, organism and drug resistance codes, sepsis and septic shock, MRSA, Zika, and COVID-19.
- Human Immunodeficiency Virus (HIV) Infections (page 19)
- Infectious agents as the cause of diseases classified to other chapters (page 22)
- Infections resistant to antibiotics (page 22)
- Sepsis, Severe Sepsis, and Septic Shock (page 23)
- Methicillin Resistant Staphylococcus aureus (MRSA) Conditions (page 27)
- Zika virus infections (page 28)
- Coronavirus infections (page 28)
Other codes under B50-B64
Protozoal diseases (B50-B64)
- B50Plasmodium falciparum malaria
- B51Plasmodium vivax malaria
- B52Plasmodium malariae malaria
- B53Other specified malaria
- B54Unspecified malaria
- B55Leishmaniasis
- B56African trypanosomiasis
- B57Chagas' disease
- B58Toxoplasmosis
- B59Pneumocystosis(this code)
- B60Other protozoal diseases, not elsewhere classified
- B64Unspecified protozoal disease
B59 MS-DRGs
As the principal diagnosis, B59 groups to these 8 MS-DRGs (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.
- DRG 177 Respiratory Infections and Inflammations with MCC
- DRG 178 Respiratory Infections and Inflammations with CC
- DRG 179 Respiratory Infections and Inflammations without CC/MCC
- DRG 791 Prematurity with Major Problems
- DRG 793 Full Term Neonate with Major Problems
- DRG 974 HIV with Major Related Condition with MCC
- DRG 975 HIV with Major Related Condition with CC
- DRG 976 HIV with Major Related Condition without CC/MCC
Related conditions
Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.
B59 is in Pneumonia (except that caused by tuberculosis) (RSP002, its default category), with 68 codes. Others in it:
Medicare coverage articles listing B59
These 8 Medicare billing and coding articles list B59 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.
- MolDX: Molecular Syndromic Panels for Infectious Disease Pathogen Identification Testing (4 contractors)
- Pharmacogenomics Testing (2 contractors)
- Computerized Axial Tomography (CT), Thorax
- Oximetry Services
- Pharmacogenomic Testing
- Respiratory Care
- Respiratory Therapy (Respiratory Care)
- Nebulizers - Policy Article
Other codes that refer to B59
Notes on these codes point to B59.
- J16 Excludes1: pneumocystosis (B59)
- J17 Excludes1: pneumocystosis (B59)
- J17 Excludes1: pneumonia due to Pneumocystis carinii (B59)
- J17 Excludes1: pneumonia due to Pneumocystis jirovecii (B59)
- J84.11 Excludes1: pneumocystis pneumonia (B59)
- J84.114 Excludes1: pneumocystis pneumonia (B59)
- J93.12 Code First: pneumonia due to Pneumocystis carinii (B59)
About the condition
Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.
Pneumocystis Infections
Pneumocystis jirovecii is a fungus that is common throughout the world. Many people have been exposed to it as children. Some people have the fungus in their lungs. If you are healthy, it usually will not make you sick. But it can make you sick if you have a weakened immune system, for example if you:
Read more about pneumocystis infections on MedlinePlusCode history
Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.
ICD-9-CM equivalent
Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).
- 136.3 Pneumocystosis