B59 — Pneumocystosis
Is B59 billable?
Yes — B59 is billable for FY2027. B59 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. B59 may be submitted for encounters from October 1, 2026 through September 30, 2027.
B59 at a glance
| Code | B59 |
|---|---|
| Description | Pneumocystosis |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does B59 group to?
B59 sits in MDC 04 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 177Respiratory Infections and Inflammations with MCCmedical
- 178Respiratory Infections and Inflammations with CCmedical
- 179Respiratory Infections and Inflammations without CC/MCCmedical
As a secondary diagnosis, B59 is a major complication or comorbidity (MCC), which can move a stay into a higher-paying DRG.
How is B59 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to B59. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Pneumocystis carinii pneumonia
- Pneumocystis jirovecii (pneumonia)
- Pneumocystosis (with pneumonia)
- Infection, infected, infective › Pneumocystis carinii (opportunistic)
- Infection, infected, infective › Pneumocystis jirovecii (opportunistic)
- Pneumonia › plasma cell (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Pneumonia › Pneumocystis (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Disease, diseased › protozoal › pneumocystosis
- Pneumonia › in › pneumocystosis (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Pneumonia › interstitial › plasma cell (acute) (double) (migratory) (purulent) (septic) (unresolved)
Inclusion terms
Alternative wording in documentation that is classified to B59.
- Pneumonia due to Pneumocystis carinii
- Pneumonia due to Pneumocystis jirovecii
Excludes1 — never code together — inherited from B50-B64
The conditions below can never be reported together with B59 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Use additional code — inherited from Chapter 1
Report an additional code alongside B59 to fully describe the condition. B59 is sequenced first.
- code to identify resistance to antimicrobial drugs (Z16.-)
Excludes2 — not included here — inherited from Chapter 1
The conditions below are not part of B59, but a patient may have both at the same time. When documentation supports it, B59 and the excluded code may both be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
How long has B59 existed?
B59 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which codes are confused with B59?
ICD-10-CM declares these codes mutually exclusive with B59 — exactly one of each pair can be correct for a given encounter.