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A18.4 vs A18.6

A18.4 (Tuberculosis of skin and subcutaneous tissue) compared with A18.6 (Tuberculosis of (inner) (middle) ear), from the official CMS tabular data.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Summary

These codes can be reported together when both conditions are documented, because A18.6 lists A18.4 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

Title wording.The titles share “Tuberculosis of”; A18.4 says “skin and subcutaneous tissue” where A18.6 says “(inner) (middle) ear”.

Registry fact

Can these codes be reported together?

Yes, when both are documented.A18.6 lists A18.4 under Excludes2: “tuberculosis of external ear (A18.4)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. A18.4 carries 7 Excludes1 notes and A18.6 carries 7 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.A18.6’s tabular entry: “tuberculosis of external ear (A18.4)”. The note covers A18.4.

Official ruleGuide: Excludes1 vs Excludes2

Is one more specific?

No.Neither is a subdivision of the other, and neither title is the unspecified form; they describe different conditions within category A18.

Registry fact

Is one a parent or header code?

No.Both are billable codes, and neither contains the other.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

A18.6
Tuberculosis of (inner) (middle) ear
↔
A18.4
Tuberculosis of skin and subcutaneous tissue

What we found

Yes, when both are documented.A18.6 carries an Excludes2 note covering A18.4: “tuberculosis of external ear (A18.4)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2027

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

Similar descriptions do not make codes interchangeable. The documentation and the official instructions decide which code applies.

Official descriptionDiffers
A18.4

Tuberculosis of skin and subcutaneous tissue

A18.6

Tuberculosis of (inner) (middle) ear

StatusSame for both
Billable
Excludes1Same for both
  • 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)
Excludes2Differs
A18.4
  • lupus erythematosus (L93.-)
  • systemic lupus erythematosus (M32.-)
A18.6
  • tuberculosis of external ear (A18.4)
  • tuberculous mastoiditis (A18.03)
Use additional codeSame for both
  • code, if applicable, for associated cachexia (E88.A)
CategorySame for both

A18 Tuberculosis of other organs

ChapterSame for both

A00-B99 — Certain Infectious and Parasitic Diseases (A00-B99)

IncludesDiffers
A18.4
  • infections due to Mycobacterium tuberculosis and Mycobacterium bovis
  • Erythema induratum, tuberculous
  • Lupus exedens
  • Lupus vulgaris NOS
A18.6
  • infections due to Mycobacterium tuberculosis and Mycobacterium bovis
  • Tuberculous otitis media

No Code first, Code also and 7th character note at either code.

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on. In a row that differs, notes every code shares are dimmed.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources