A18.4 ICD-10-CM Code: Tuberculosis of skin and subcutaneous tissue
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Tuberculosis (A15-A19)
A18.4
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceTuberculosis of skin and subcutaneous tissue
This is a form of tuberculosis that affects the skin and the tissues just beneath the skin surface, causing lesions or sores. It occurs when the tuberculosis bacteria spreads to these outer body areas rather than staying in the lungs.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Erythema induratum, tuberculous
- Lupus exedens
- Lupus vulgaris NOS
- Lupus vulgaris of eyelid
- Scrofuloderma
Excludes 2
Official- lupus erythematosus (L93.-)
- systemic lupus erythematosus (M32.-)
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A18.4 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A18.4 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A18.4 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A18.4 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A18.4 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is A18.4 an HCC code?
No. A18.4 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A18.4 is the ICD-10-CM diagnosis code for tuberculosis of skin and subcutaneous tissue. This is a form of tuberculosis that affects the skin and the tissues just beneath the skin surface, causing lesions or sores. It occurs when the tuberculosis bacteria spreads to these outer body areas rather than staying in the lungs. A18.4 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering tuberculosis (a15-a19).
A18.4 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Verify documentation specifies tuberculosis involvement of skin/subcutaneous tissue; do not use this code for other skin conditions or non-tuberculous infections.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A18.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify documentation specifies tuberculosis involvement of skin/subcutaneous tissue; do not use this code for other skin conditions or non-tuberculous infections
- •This code may require an additional code to identify the site of infection (e.g., face, trunk, extremity) if the documentation provides this level of specificity