A31.1 ICD-10-CM Code: Cutaneous mycobacterial infection

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for A31.1 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on A31.1 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for A31.1

MedCoder structured workflow — derived from this code’s own official record

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Official instructions as workflow

• Excludes2 — not part of A31.1(2 notes)

  Coding workflow: The conditions named in this note are not included in A31.1. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareA30

  See the official tabular notes · Guidelines I.A.12.b

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Indexed Clinical Terms (14)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

• 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

Don’t confuse A31.1 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of A31.1 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• A31.9— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “Mycobacterial infection, unspecified” takes A31.9; specificity in the record moves it back here.

  Full comparison: A31.1 vs A31.9 →

• A30— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of leprosy adds A30; it is not part of this code and both may be reported when both are documented.

  Full comparison: A31.1 vs A30 →

• A15— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of tuberculosis adds A15; it is not part of this code and both may be reported when both are documented.

  Full comparison: A31.1 vs A15 →

• A19— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of tuberculosis adds A19; it is not part of this code and both may be reported when both are documented.

  Full comparison: A31.1 vs A19 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• CC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 5 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 2 MS-DRGs: DRG 606 (MDC 09), DRG 607 (MDC 09).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):SKN001 — Skin and subcutaneous tissue infections (default); INF003 — Bacterial infections.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

A31.0 — Pulmonary mycobacterial infection, A31.2 — Disseminated mycobacterium avium-intracellulare complex (DMAC), A31.8 — Other mycobacterial infections, A31.9 — Mycobacterial infection, unspecified

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Skin and subcutaneous tissue infections, Bacterial infections).

A20.1 — Cellulocutaneous plague, A21.0 — Ulceroglandular tularemia, A22.0 — Cutaneous anthrax, A36.3 — Cutaneous diphtheria, A43.1 — Cutaneous nocardiosis, A46 — Erysipelas, A51.39 — Other secondary syphilis of skin, H05.011 — Cellulitis of right orbit, H05.012 — Cellulitis of left orbit, H05.013 — Cellulitis of bilateral orbits, H05.019 — Cellulitis of unspecified orbit, L00 — Staphylococcal scalded skin syndrome, L01.00 — Impetigo, unspecified, L01.01 — Non-bullous impetigo, L01.02 — Bockhart's impetigo, L01.03 — Bullous impetigo, L01.09 — Other impetigo, L01.1 — Impetiginization of other dermatoses, L02.01 — Cutaneous abscess of face, L02.02 — Furuncle of face, +543 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Granuloma”, “Mycobacterium, mycobacterial”; these codes share that main term but sit in a different category of the Tabular List.

A18.01 — Tuberculosis of spine (spine, tuberculous), A30.9 — Leprosy, unspecified (leprae), A52.19 — Other symptomatic neurosyphilis (spine, syphilitic), A58 — Granuloma inguinale (vagina), A66.4 — Gummata and ulcers of yaws (tropicum), B35.8 — Other dermatophytoses (Majocchi's), B37.2 — Candidiasis of skin and nail (monilial), B38.1 — Chronic pulmonary coccidioidomycosis (coccidioidal, lung), B38.4 — Coccidioidomycosis meningitis (coccidioidal, meninges), B38.7 — Disseminated coccidioidomycosis (coccidioidal), B41.8 — Other forms of paracoccidioidomycosis (paracoccidioidal), B65.9 — Schistosomiasis, unspecified (brain, schistosomiasis), B83.9 — Helminthiasis, unspecified (peritoneum, due to ova of helminths NOS), B99.8 — Other infectious disease (infectious, specified NEC), B99.9 — Unspecified infectious disease (infectious), C81.9 — Hodgkin lymphoma, unspecified (Hodgkin), C96.6 — Unifocal Langerhans-cell histiocytosis (bone, lung), D76.3 — Other histiocytosis syndromes (reticulohistiocytic), D86.89 — Sarcoidosis of other sites (hepatic NEC, in, sarcoidosis), G06.0 — Intracranial abscess and granuloma (brain), +42 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

HIV Screening Test

Contextual Map

Every relationship of A31.1 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

• A00-B99 — Chapter 1: Certain Infectious and Parasitic Diseases (A00-B99) (A00-B99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• A30-A49 — Other bacterial diseases[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Clinical classification (CCSR)

• SKN001 — Skin and subcutaneous tissue infections[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)
• INF003 — Bacterial infections[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• CC — Complication or Comorbidity [MS-DRG severity]: “As a secondary diagnosis this code can raise the stay's MS-DRG severity tier (CC).”— CMS MS-DRG Definitions Manual (Appendix C) · FY2026
• DRG 606 — MINOR SKIN DISORDERS WITH MCC[MS-DRG]: “MINOR SKIN DISORDERS WITH MCC (MDC 09)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 607 — MINOR SKIN DISORDERS WITHOUT MCC[MS-DRG]: “MINOR SKIN DISORDERS WITHOUT MCC (MDC 09)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 09 — Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast[MDC crossing]: “Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 7,376 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries (14)

• Buruli ulcer[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Disease, diseased, swimming-pool granuloma[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Granuloma, swimming pool[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Infection, infected, infective (opportunistic), Bacillus, swimming pool[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Infection, infected, infective (opportunistic), swimming pool bacillus[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Mycobacterium, mycobacterial (infection), atypical, cutaneous[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Mycobacterium, mycobacterial (infection), balnei[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Mycobacterium, mycobacterial (infection), cutaneous[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• and 6 more

Nearest codes

• A31 — Infection due to other mycobacteria[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• A31.0 — Pulmonary mycobacterial infection[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• A31.2 — Disseminated mycobacterium avium-intracellulare complex (DMAC)[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• A31.8 — Other mycobacterial infections[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• A31.9 — Mycobacterial infection, unspecified[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Inpatient payment groups Official source data

CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to A31.1 in its code family, with their registry titles.

• A31 — Infection due to other mycobacteria
• A31.0 — Pulmonary mycobacterial infection
• A31.2 — Disseminated mycobacterium avium-intracellulare complex (DMAC)
• A31.8 — Other mycobacterial infections
• A31.9 — Mycobacterial infection, unspecified

View all codes in the A31 family