Question 1

What is ICD-10 code L99?

Accepted Answer

L99 is the ICD-10-CM diagnosis code for other disorders of skin and subcutaneous tissue in diseases classified elsewhere. Skin and tissue disorders that occur as a result of another disease classified elsewhere in the medical coding system. L99 sits in the ICD-10-CM chapter for diseases of the skin and subcutaneous tissue (l00-l99), within the section covering other disorders of the skin and subcutaneous tissue (l80-l99).

L99 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.

This is a secondary code; always code the primary underlying disease first.

Question 2

Is L99 an HCC code?

Accepted Answer

No. L99 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is L99 billable?

Accepted Answer

Yes. L99 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. L99 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for L99?

Accepted Answer

L99 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither community model rewards L99 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

Question 5

What should coders know when reporting L99?

Accepted Answer

This is a secondary code; always code the primary underlying disease first Use this code only when the skin condition is a manifestation of another classified disease

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L99

Is L99 an HCC code?

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L99 ICD-10-CM Code: Other disorders of skin and subcutaneous tissue in diseases classified elsewhere

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L99

Is L99 an HCC code?

Get the V28 RAF + MEAT cheat sheet

What This Code Means

Coding Tips

Excludes 1, Do NOT code together

Code First

Code Hierarchy

Work L99 in HCC Buddy