2027 ICD-10-CM Diagnosis Code A31.9Mycobacterial infection, unspecified
ICD-10-CM Codes›A00–B99›A30-A49›A31
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
A31.9 is a billable ICD-10-CM diagnosis code for mycobacterial infection, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 867 through 869, 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 5 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Abscess of spinal cord caused by bacterium
- Abscess of spinal epidural space caused by bacterium
- Abscess of spinal epidural space caused by Mycobacterium
- Acid-fast bacteria present
- Arthropathy associated with bacterial disease
- Atypical mycobacterial infection
- Atypical mycobacterial infection of hand
- Disseminated atypical infection caused by Mycobacterium co-occurrent with human immunodeficiency virus infection
- Disseminated atypical mycobacterial infection
- Disseminated mycobacteriosis
- Granuloma of spinal cord caused by bacterium
- Granuloma of spinal cord caused by Mycobacterium
- Infection caused by Mycobacterium resistant to multiple antimycobacterial agents
- Infection caused by Mycobacteroides abscessus
- Mycobacterial gastritis
- Mycobacterial infection
- Mycobacterial infection of the central nervous system
- Mycobacterial postinfective arthritis
- Mycobacterial spinal cord abscess
- Mycobacteriosis
- Mycobacteriosis with AIDS
- Post-bacterial arthropathy
- Reactive arthritis due to and following mycobacteriosis
- Recurrent infection caused by Mycobacterium
- Skin and soft tissue atypical mycobacterial infection
- Spinal epidural abscess
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to A31.9: its own notes plus those printed at A31 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Atypical mycobacterial infection NOS
- Mycobacteriosis NOS
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may 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)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Index to Diseases and InjuriesGuidance
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Mycobacterial Infection
infection due to organisms from the genus mycobacteria.
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 A31.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About A31.9Overview
What is the ICD-10 code for mycobacterial infection, unspecified?
The ICD-10-CM code for mycobacterial infection, unspecified is A31.9 (sometimes written as A319). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is A31.9 (Infection due to other mycobacteria) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report mycobacterial infection, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does A31.9 group to?
When mycobacterial infection, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 974, 976, 975, 867, 869, 868, with relative weights from 0.6784 to 3.0488 depending on complications. Higher weights mean higher Medicare reimbursement.
Is A31.9 a CC or MCC?
CMS lists A31.9 as a CC (complication or comorbidity) for FY 2027. 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 5 closely related codes in its exclusion list.
What is the ICD-9 equivalent of A31.9?
Under the General Equivalence Mappings, mycobacterial infection, unspecified converts to ICD-9-CM 031.9 (mycobacterial dis NOS). The mapping is a direct match.
