2026 ICD-10-CM Diagnosis Code A31.1Cutaneous mycobacterial infection

ICD-10-CM Codes›A00–B99›A30-A49›A31

ICD-10-CM A31.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A31.1 is a billable ICD-10-CM diagnosis code for cutaneous mycobacterial infection. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 606 through 607. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Skin and subcutaneous tissue infections.

Code Identity

ICD-10-CM Code
A31.1
Billable Status
Yes — Valid for Submission
Code Describes
Cutaneous mycobacterial infection
Short Description
Cutaneous mycobacterial infection
Same as the full description in the CMS dataset.
Parent Code
A31
Infection due to other mycobacteria

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA31Infection due to other mycobacteria
This CodeA31.1Cutaneous mycobacterial infection

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Buruli ulcer
  • Cutaneous infectious disease caused by Mycobacteria
  • Cutaneous mycobacterium marinum infection
  • Dermatosis secondary to peripheral nerve disorder
  • Fish tank granuloma
  • Hyperimmune cutaneous reaction to atypical mycobacteria
  • Hyperimmune cutaneous reaction to mycobacterium avium-intracellulare
  • Infection caused by Mycobacterium chelonei
  • Infection caused by Mycobacterium gordonae
  • Infection caused by Mycobacterium haemophilum
  • Infection caused by Mycobacterium malmoense
  • Infection caused by Mycobacterium marinum
  • Infection caused by Mycobacterium scrofulaceum
  • Infection caused by Mycobacterium szulgai
  • Infection caused by Mycobacteroides abscessus
  • Infection of skin caused by Mycobacterium haemophilum
  • Mycobacterium avium intracellulare infection of skin
  • Mycobacterium fortuitum infection of skin
  • Mycobacterium gordonae infection of skin
  • Mycobacterium malmoense infection of skin
  • Mycobacterium scrofulaceum infection of skin
  • Mycobacterium szulgai infection of skin
  • Mycobacteroides abscessus infection of skin
  • Mycobacteroides chelonae infection of skin
  • Neuropathic ulceration of skin caused by Mycobacterium leprae
  • Non-pyogenic bacterial infection of skin

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Buruli ulcer
  • Infection due to Mycobacterium marinum
  • Infection due to Mycobacterium ulcerans

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Buruli ulcer
    • Disease, diseased
      • swimming-pool granuloma
    • Granuloma
      • swimming pool
    • Infection, infected, infective(opportunistic)
      • Bacillus
        • swimming pool
    • Infection, infected, infective(opportunistic)
      • swimming pool bacillus
    • Mycobacterium, mycobacterial(infection)
      • atypical
        • cutaneous
    • Mycobacterium, mycobacterial(infection)
      • balnei
    • Mycobacterium, mycobacterial(infection)
      • cutaneous
    • Mycobacterium, mycobacterial(infection)
      • luciflavum
    • Mycobacterium, mycobacterial(infection)
      • marinum (M. balnei)
    • Mycobacterium, mycobacterial(infection)
      • ulcerans
    • Ulcer, ulcerated, ulcerating, ulceration, ulcerative
      • Buruli
    • Ulcer, ulcerated, ulcerating, ulceration, ulcerative
      • mycobacterial (skin)
    • Ulcer, ulcerated, ulcerating, ulceration, ulcerative
      • skin (atrophic) (chronic) (neurogenic) (non-healing) (perforating) (pyogenic) (trophic) (tropical)
        • mycobacterial

Clinical ClassificationClinical

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

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR SKN001
Skin and subcutaneous tissue infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Buruli Ulcer

    a lesion in the skin and subcutaneous tissues due to infections by mycobacterium ulcerans. it was first reported in uganda, africa.

  • Mycobacterium ulcerans

    a slow-growing mycobacterium that infects the skin and subcutaneous tissues, giving rise to indolent buruli ulcer.

  • Buruli Ulcer

    a cutaneous infection caused by mycobacterium ulcerans. it presents with painless nodular swelling of the skin, leading to the formation of necrotizing ulcers.

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 A31.1 to ICD-9-CMHistory

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

ICD-9-CM
031.1 Cutaneous mycobacteria
Exact Match The mapping is direct, with no qualifiers.

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 A31.1Overview

Is A31.1 (Infection due to other mycobacteria) a billable code?

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

What MS-DRG does A31.1 group to?

When cutaneous mycobacterial infection is the principal diagnosis on an inpatient stay, it groups to MS-DRG 606, 607, with relative weights from 0.9064 to 1.5132 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A31.1?

Under the General Equivalence Mappings, cutaneous mycobacterial infection converts to ICD-9-CM 031.1 (cutaneous mycobacteria). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.