D81.4
BillableNezelof's syndrome
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D81.4 an HCC code?
Yes. D81.4 maps to Specified Immunodeficiencies and White Blood Cell Disorders under the CMS-HCC V28 risk adjustment model (and Disorders of Immunity under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for D81.4
For D81.4to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed D81.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D81.4 is the ICD-10-CM diagnosis code for nezelof's syndrome. A rare inherited immune disorder characterized by low T-cell counts and normal B-cell counts, causing increased susceptibility to infections. D81.4 sits in the ICD-10-CM chapter for diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89), within the section covering certain disorders involving the immune mechanism (d80-d89).
Under the CMS-HCC V28 risk adjustment model, D81.4 maps to Specified Immunodeficiencies and White Blood Cell Disorders (HCC 115) with a community, non-dual, aged base RAF weight of 0.565. Under the older CMS-HCC V24 model, D81.4 maps to Disorders of Immunity (HCC 47) with a community, non-dual, aged base RAF weight of 0.665. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Confirm diagnosis through immunological testing showing T-cell lymphopenia with normal B-cells. Because D81.4 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for D81.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm diagnosis through immunological testing showing T-cell lymphopenia with normal B-cells
- •Document any associated features such as thymic abnormalities or developmental delays
Clinical Significance
Nezelof syndrome is a rare primary T-cell immunodeficiency characterized by thymic hypoplasia with reduced T-cell numbers and function but normal or near-normal B-cell numbers and immunoglobulin levels. Unlike SCID, patients may have some residual T-cell function, but they remain vulnerable to opportunistic infections, particularly viral and fungal pathogens, and may develop autoimmune manifestations.
Documentation Requirements
- ✓Documentation must include T-cell enumeration showing reduced CD3+ T-cells, normal B-cell counts, immunoglobulin levels (which may be normal despite impaired T-cell help), thymic imaging or biopsy results if available, clinical infection history, and treatment plan.
- ✓Document that the condition does not meet full SCID criteria to justify use of D81.4 rather than a D81.0-D81.2 code.
Commonly Confused Codes
- •D81.2 (severe combined immunodeficiency with low or normal B-cells, which is more severe with complete T-cell absence), D82.1 (DiGeorge syndrome which also involves thymic hypoplasia but with characteristic cardiac and facial features), D81.9 (combined immunodeficiency, unspecified), D83.1 (common variable immunodeficiency with T-cell disorders, which has different diagnostic criteria).