2026 ICD-10-CM Diagnosis Code A31.0Pulmonary mycobacterial infection
ICD-10-CM Codes›A00–B99›A30-A49›A31
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 6
- Not Chronic
A31.0 is a billable ICD-10-CM diagnosis code for pulmonary mycobacterial infection. 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. 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 122 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Pneumonia (except that caused by tuberculosis).
For Medicare Advantage risk adjustment, A31.0 maps to CMS-HCC Category 6 (Opportunistic Infections) under the V28 model, adding a risk factor of about 0.381 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
A31.0 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
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.
- Atypical mycobacterial infection of lung
- Battey disease
- Disseminated atypical mycobacterial infection
- Disseminated Mycobacterium kansasii infection
- Hyperimmune cutaneous reaction to atypical mycobacteria
- Hyperimmune cutaneous reaction to mycobacterium kansasii
- Infection caused by Mycobacterium intracellulare
- Infection caused by Mycobacterium kansasii
- Infection caused by Mycobacterium malmoense
- Infection caused by Mycobacterium xenopi
- Infection of lung caused by Mycobacterium kansasii
- Infection of lung caused by Mycobacterium malmoense
- Infection of lung caused by Mycobacterium xenopi
- Lady Windermere syndrome
- Mycobacterial pneumonia
- Mycobacterium kansasii infection of skin
- Non-tuberculous mycobacterial pneumonia
- Pulmonary disease caused by Mycobacteria
- Pulmonary Mycobacterium avium complex infection
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Infection due to Mycobacterium avium
- Infection due to Mycobacterium intracellulare [Battey bacillus]
- Infection due to Mycobacterium kansasii
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
Infection, infected, infective (opportunistic) B99.9
lung See Also: Pneumonia; J18.9
atypical Mycobacterium A31.0
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Mycobacterial Infections
Mycobacteria are a type of germ. There are many different kinds. The most common one causes tuberculosis. Another one causes leprosy. Still others cause infections that are called atypical mycobacterial infections. They aren't "typical" because they don't cause tuberculosis.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert A31.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About A31.0Overview
What is the ICD-10 code for pulmonary mycobacterial infection?
The ICD-10-CM code for pulmonary mycobacterial infection is A31.0 (sometimes written as A310). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is A31.0 (Infection due to other mycobacteria) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report pulmonary mycobacterial infection on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does A31.0 group to?
When pulmonary mycobacterial infection is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, with relative weights from 0.7550 to 1.5627 depending on complications. Higher weights mean higher Medicare reimbursement.
Is A31.0 a CC or MCC?
CMS lists A31.0 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 122 closely related codes in its exclusion list.
What is the ICD-9 equivalent of A31.0?
Under the General Equivalence Mappings, pulmonary mycobacterial infection converts to ICD-9-CM 031.0 (pulmonary mycobacteria). The mapping is a direct match.
What HCC is A31.0?
A31.0 (pulmonary mycobacterial infection) maps to CMS-HCC Category 6 (Opportunistic Infections), commonly written as HCC 6, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 6 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 5.
Does A31.0 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, A31.0 adds a risk adjustment factor of about 0.381 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.381 to 0.833 depending on the payment segment). HCC 6 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 6 category page.
