2026 ICD-10-CM Diagnosis Code A43.0Pulmonary nocardiosis

ICD-10-CM Codes›A00–B99›A30-A49›A43

ICD-10-CM A43.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A43.0 is a billable ICD-10-CM diagnosis code for pulmonary nocardiosis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179, 974 through 976. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 10 closely related codes. Coders also document this condition as nocardial pneumonia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Pneumonia (except that caused by tuberculosis).

A43.0 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 115 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 115, ESRD (V21) category 115, and ESRD (V24) category 115 for payment year 2026.

Code Identity

ICD-10-CM Code
A43.0
Billable Status
Yes — Valid for Submission
Code Describes
Pulmonary nocardiosis
Short Description
Pulmonary nocardiosis
Same as the full description in the CMS dataset.
Parent Code
A43
Nocardiosis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA43Nocardiosis
This CodeA43.0Pulmonary nocardiosis

Medicare Risk Adjustment (HCC)Billing

A43.0 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 115
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 115 · ESRD (V21): HCC 115 · ESRD (V24): HCC 115
ESRD V21 weights: 0.013 dialysis, 0.143–0.155 functioning graft · ESRD V24 weights: 0.030 dialysis, 0.154–0.248 functioning graft
Part D (RxHCC)
Not mapped
A43.0 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Nocardial pneumonia
  • Pulmonary nocardiosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR RSP002
Pneumonia (except that caused by tuberculosis)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A43.0 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
039.1 Pulmonary actinomycosis
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A43.0Overview

What is the ICD-10 code for pulmonary nocardiosis?

The ICD-10-CM code for pulmonary nocardiosis is A43.0 (sometimes written as A430). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A43.0 (Nocardiosis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report pulmonary nocardiosis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A43.0 group to?

When pulmonary nocardiosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, 974, 975, 976, with relative weights from 0.7550 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A43.0 a CC or MCC?

CMS lists A43.0 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 10 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A43.0?

Under the General Equivalence Mappings, pulmonary nocardiosis converts to ICD-9-CM 039.1 (pulmonary actinomycosis). The mapping is approximate, so confirm the match fits the documentation.

Does A43.0 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. A43.0 mapped to HCC 115 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess), ESRD (V21) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess), and ESRD (V24) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess).