2026 ICD-10-CM Diagnosis Code A18.4Tuberculosis of skin and subcutaneous tissue

ICD-10-CM Codes›A00–B99›A15-A19›A18

ICD-10-CM A18.4
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A18.4 is a billable ICD-10-CM diagnosis code for tuberculosis of skin and subcutaneous tissue. 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, 974 through 976. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Tuberculosis.

Code Identity

ICD-10-CM Code
A18.4
Billable Status
Yes — Valid for Submission
Code Describes
Tuberculosis of skin and subcutaneous tissue
Short Description
Tuberculosis of skin and subcutaneous tissue
Same as the full description in the CMS dataset.
Parent Code
A18
Tuberculosis of other organs

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA15-A19Tuberculosis
CategoryA18Tuberculosis of other organs
This CodeA18.4Tuberculosis of skin and subcutaneous tissue

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute tuberculous ulcer
  • BCG-induced lupus vulgaris
  • BCG-induced scrofuloderma
  • BCG-induced tuberculide
  • Cutaneous complication of BCG immunization
  • Cutaneous tuberculous gumma
  • Erythema induratum
  • Erythema nodosum due to bacterial infection
  • Erythema nodosum due to tuberculosis
  • Infection caused by Mycobacterium bovis
  • Infection following immunization
  • Lobular panniculitis
  • Lupus vulgaris
  • Lupus vulgaris of nose
  • Nodular tuberculide
  • Papular tuberculide
  • Scrofuloderma
  • Tuberculid
  • Tuberculoma
  • Tuberculosis cutis indurativa
  • Tuberculosis cutis lichenoides
  • Tuberculosis of skin
  • Tuberculosis of skin and subcutaneous tissue
  • Tuberculosis of subcutaneous cellular tissue
  • Tuberculosis papulonecrotica
  • Tuberculosis verrucosa cutis
  • Tuberculous abscess
  • Tuberculous abscess of neck
  • Tuberculous chancre
  • Vaccination site lump

Tabular List NotesGuidance

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

Inclusion Terms

  • Erythema induratum, tuberculous
  • Lupus exedens
  • Lupus vulgaris NOS
  • Lupus vulgaris of eyelid
  • Scrofuloderma
  • Tuberculosis of external ear

Type 2 Excludes

  • lupus erythematosus L93
  • systemic lupus erythematosus M32

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.

    • Acnitis(primary)
    • Bazin's disease(primary) (tuberculous)
    • Cellulitis(diffuse) (phlegmonous) (septic) (suppurative)
      • tuberculous (primary)
    • Erythema, erythematous(infectional) (inflammation)
      • induratum (nontuberculous)
        • tuberculous
    • Erythema, erythematous(infectional) (inflammation)
      • nodosum
        • tuberculous
    • Erythema, erythematous(infectional) (inflammation)
      • tuberculous (primary)
    • Gumma(syphilitic)
      • scrofulous (tuberculous)
    • Gumma(syphilitic)
      • tuberculous
    • Lichen
      • scrofulosus (primary) (tuberculous)
    • Lichenoides tuberculosis(primary)
    • Lupus
      • exedens
    • Lupus
      • tuberculous
    • Lupus
      • tuberculous
        • eyelid
    • Lupus
      • vulgaris
    • Lupus
      • vulgaris
        • eyelid
    • Paronychia
      • tuberculous (primary)
    • Scrofulide(primary) (tuberculous)
    • Scrofuloderma, scrofulodermia(any site) (primary)
    • Scrofulosus lichen(primary) (tuberculous)
    • Tarsitis(eyelid)
      • tuberculous
    • Tuberculid, tuberculide(indurating, subcutaneous) (lichenoid) (miliary) (papulonecrotic) (primary) (skin)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • abscess (respiratory)
        • skin (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • cellulitis (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • colliquativa (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • cutis (colliquativa) (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • ear (inner) (middle)
        • external (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • ear (inner) (middle)
        • skin (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • erythema (induratum) (nodosum) (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • eyelid (primary) (lupus)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • indurativa (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • lichenoides (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • lupus vulgaris
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • papulonecrotic (a) (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • paronychia (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • skin (any site) (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • subcutaneous tissue (cellular) (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • subcutis (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • tarsitis
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • ulcer (skin) (primary)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • verruca, verrucosa (cutis) (primary)
    • Ulcer, ulcerated, ulcerating, ulceration, ulcerative
      • skin (atrophic) (chronic) (neurogenic) (non-healing) (perforating) (pyogenic) (trophic) (tropical)
        • tuberculous (primary)
    • Ulcus
      • cutis tuberculosum
    • Verruca(due to HPV) (filiformis) (simplex) (viral) (vulgaris)
      • necrogenica (primary) (tuberculosa)
    • Verruca(due to HPV) (filiformis) (simplex) (viral) (vulgaris)
      • tuberculosa (primary)
    • Wart(due to HPV) (filiform) (infectious) (viral)
      • prosector (tuberculous)
    • Wart(due to HPV) (filiform) (infectious) (viral)
      • tuberculous

Clinical ClassificationClinical

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

CCSR INF001
Tuberculosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Lupus Vulgaris

    a form of cutaneous tuberculosis. it is seen predominantly in women and typically involves the nasal mucosa; buccal mucosa; and conjunctival mucosa.

  • Tuberculoma

    a tumor-like mass resulting from the enlargement of a tuberculous lesion.

  • Tuberculoma, Intracranial

    a well-circumscribed mass composed of tuberculous granulation tissue that may occur in the cerebral hemispheres, cerebellum, brain stem, or perimeningeal spaces. multiple lesions are quite common. management of intracranial manifestations vary with lesion site. intracranial tuberculomas may be associated with seizures, focal neurologic deficits, and intracranial hypertension. spinal cord tuberculomas may be associated with localized or radicular pain, weakness, sensory loss, and incontinence. tuberculomas may arise as opportunistic infections, but also occur in immunocompetent individuals.

  • Erythema Induratum

    a type of panniculitis characterized histologically by the presence of granulomas, vasculitis, and necrosis. it is traditionally considered to be the tuberculous counterpart of nodular vasculitis, but is now known to occur without tuberculous precedent. it is seen most commonly in adolescent and menopausal women, is initiated or exacerbated by cold weather, and typically presents as one or more recurrent erythrocyanotic nodules or plaques on the calves. the nodules may progress to form indurations, ulcerations, and scars.

  • Tuberculous Abscess

    an abscess resulting from infection by mycobacterium tuberculosis.

Patient EducationClinical

Skin Infections

Your skin is your body's largest organ. It has many different functions, including covering and protecting your body. It helps keep germs out. But sometimes the germs can cause a skin infection. It often happens when the germs enter your body through a break, cut, or wound on your skin.

The full article covers:

  • What are skin infections?
  • What causes skin infections?
  • Who is more likely to get a skin infection?
  • What are the symptoms of skin infections?
  • How are skin infections diagnosed?
  • How are skin infections treated?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A18.4 to ICD-9-CMHistory

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

ICD-9-CM
017.00 TB skin/subcutan-unspec
Approximate The match is approximate rather than exact.
ICD-9-CM
017.10 Erythema nodos tb-unspec
Approximate The match is approximate rather than exact.

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 A18.4Overview

Is A18.4 (Tuberculosis of other organs) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report tuberculosis of skin and subcutaneous tissue on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A18.4 group to?

When tuberculosis of skin and subcutaneous tissue is the principal diagnosis on an inpatient stay, it groups to MS-DRG 606, 607, 974, 975, 976, with relative weights from 0.8945 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A18.4?

Under the General Equivalence Mappings, tuberculosis of skin and subcutaneous tissue converts to ICD-9-CM 017.00 (TB skin/subcutan-unspec) and 017.10 (erythema nodos tb-unspec). The mapping is approximate, so confirm the match fits the documentation.

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.