2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 606 through 607, 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 50 closely related codes. 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
  • Infective panniculitis
  • 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A18.4: its own notes plus those printed at block A15-A19 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.

From Block A15-A19 Tuberculosis applies to 51 codes
  • infections due to Mycobacterium tuberculosis and Mycobacterium bovis
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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.

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

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block A15-A19 Tuberculosis applies to 51 codes
  • congenital tuberculosis (P37.0)
  • nonspecific reaction to test for tuberculosis without active tuberculosis (R76.1-)
  • pneumoconiosis associated with tuberculosis, any type in A15 (J65)
  • positive PPD (R76.11)
  • positive tuberculin skin test without active tuberculosis (R76.11)
  • sequelae of tuberculosis (B90.-)
  • silicotuberculosis (J65)

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.

On A18.4 itself
  • lupus erythematosus (L93.-)
  • systemic lupus erythematosus (M32.-)
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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.

From Block A15-A19 Tuberculosis applies to 51 codes
  • code, if applicable, for associated cachexia (E88.A)
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A18.4, its category, or a range that includes it.

Applicable To 1

These notes mention A18.4.

  • O98.0 Tuberculosis complicating pregnancy, childbirth and the puerperium
    Conditions in A15-A19 names A15-A19, which includes this code

Excludes1 3

These codes carry an Excludes1 note naming A18.4: they are not reported together with it, unless the two conditions are unrelated.

  • L52 Erythema nodosum
    tuberculous erythema nodosum (A18.4)
  • L93 Lupus erythematosus
    lupus exedens (A18.4)
  • L93 Lupus erythematosus
    lupus vulgaris (A18.4)

Excludes2 3

These codes carry an Excludes2 note naming A18.4: its condition is not part of those codes, and both may be reported when the patient has both.

  • A18.5 Tuberculosis of eye
    lupus vulgaris of eyelid (A18.4)
  • A18.6 Tuberculosis of (inner) (middle) ear
    tuberculosis of external ear (A18.4)
  • A31 Infection due to other mycobacteria
    tuberculosis (A15-A19) names A15-A19, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

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

Clinical InformationClinical

  • 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.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A18.4Overview

What is the ICD-10 code for tuberculosis of skin and subcutaneous tissue?

The ICD-10-CM code for tuberculosis of skin and subcutaneous tissue is A18.4 (sometimes written as A184). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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 974, 976, 607, 975, 606, with relative weights from 0.7879 to 3.0488 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A18.4 a CC or MCC?

CMS lists A18.4 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 50 closely related codes in its exclusion list.

Can A18.4 be reported with P37.0?

Not as a rule. The Excludes1 note at block A15-A19, which applies to A18.4, lists "congenital tuberculosis (P37.0)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).