ICD-10-CM 2027
ICD-10 code for mycobacterium
From the official ICD-10-CM alphabetic index entry “Mycobacterium, mycobacterial (infection)”. Page updated September 29, 2026.
About coding mycobacterium
The ICD-10-CM code for mycobacterium is A31.9 (Mycobacterial infection, unspecified). The official index lists 28 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on A31.9.
Within A31, choose A31.9 (Mycobacterial infection, unspecified) only when documentation doesn't support a more specific option: pulmonary mycobacterial infection (A31.0), cutaneous mycobacterial infection (A31.1), disseminated mycobacterium avium-intracellulare complex (DMAC) (A31.2) and other mycobacterial infections (A31.8).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235), DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), DRG 974 (HIV with Major Related Condition with MCC, relative weight 3.0506), DRG 975 (HIV with Major Related Condition with CC, relative weight 1.3252) and DRG 976 (HIV with Major Related Condition without CC/MCC, relative weight 0.8124), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites) and MDC 25 (Human Immunodeficiency Virus Infections), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific mycobacterium codes (official index)
- anonymous A31.9 — Mycobacterial infection, unspecified
- atypical A31.9 — Mycobacterial infection, unspecified
- cutaneous A31.1 — Cutaneous mycobacterial infection
- pulmonary A31.0 — Pulmonary mycobacterial infection
- tuberculous
- specified site NEC A31.8 — Other mycobacterial infections
- avium (intracellulare complex) A31.0 — Pulmonary mycobacterial infection
- balnei A31.1 — Cutaneous mycobacterial infection
- Battey A31.0 — Pulmonary mycobacterial infection
- chelonei A31.8 — Other mycobacterial infections
- cutaneous A31.1 — Cutaneous mycobacterial infection
- extrapulmonary systemic A31.8 — Other mycobacterial infections
- fortuitum A31.8 — Other mycobacterial infections
- intracellulare (Battey bacillus) A31.0 — Pulmonary mycobacterial infection
- kansasii (yellow bacillus) A31.0 — Pulmonary mycobacterial infection
- kakaferifu A31.8 — Other mycobacterial infections
- kasongo A31.8 — Other mycobacterial infections
- leprae A30.9 — Leprosy, unspecified
- luciflavum A31.1 — Cutaneous mycobacterial infection
- marinum (M. balnei) A31.1 — Cutaneous mycobacterial infection
- nonspecific
- pulmonary (atypical) A31.0 — Pulmonary mycobacterial infection
- tuberculous
- scrofulaceum A31.8 — Other mycobacterial infections
- simiae A31.8 — Other mycobacterial infections
- systemic, extrapulmonary A31.8 — Other mycobacterial infections
- szulgai A31.8 — Other mycobacterial infections
- terrae A31.8 — Other mycobacterial infections
- triviale A31.8 — Other mycobacterial infections
- tuberculosis (human, bovine)
- ulcerans A31.1 — Cutaneous mycobacterial infection
- xenopi A31.8 — Other mycobacterial infections
Common questions about mycobacterium ICD-10 codes
What is the ICD-10 code for mycobacterium?
- A31.9 — Mycobacterial infection, unspecified. More specific codes apply when the documentation supports them: A31.9, A31.9, A31.1, A31.0 and others below.
What is the ICD-10 code for anonymous mycobacterium?
- A31.9 — Mycobacterial infection, unspecified.
What is the ICD-10 code for atypical mycobacterium?
- A31.9 — Mycobacterial infection, unspecified.
What is the ICD-10 code for avium mycobacterium?
- A31.0 — Pulmonary mycobacterial infection.
What is the ICD-10 code for balnei mycobacterium?
- A31.1 — Cutaneous mycobacterial infection.
What is the ICD-10 code for battey mycobacterium?
- A31.0 — Pulmonary mycobacterial infection.
What is the ICD-10 code for chelonei mycobacterium?
- A31.8 — Other mycobacterial infections.
Is A31.9 billable?
- Yes. A31.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A31.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A31.9 as a principal diagnosis.
Is A31.9 a CC or MCC?
- A31.9 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.