D81.4 ICD-10-CM Code: Nezelof's syndrome
D81.4 maps to CMS-HCC V28 115. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) / Certain disorders involving the immune mechanism (D80-D89)
D81.4
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceNezelof's syndrome
A rare inherited immune disorder characterized by low T-cell counts and normal B-cell counts, causing increased susceptibility to infections.
Buddy Insight
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.
CMS-HCC V28
MappedHCC 115
Coefficient HCC 115: 0.565 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 073
Code-level coefficient reference
ESRD/PACE
MappedHCC 47
Code-level coefficient reference
RXHCC
MappedHCC 99
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for D81.4. Check the code and parent instructions in the Code Book.
Excludes 2
Official- autoimmune disease (systemic) NOS (M35.9)Inherited from D50-D89
- certain conditions originating in the perinatal period (P00-P96)Inherited from D50-D89
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from D50-D89
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from D50-D89
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from D50-D89
- human immunodeficiency virus [HIV] disease (B20)Inherited from D50-D89
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from D50-D89
- neoplasms (C00-D49)Inherited from D50-D89
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from D50-D89
Related Codes
Includes
Official- defects in the complement systemInherited from D80-D89
- immunodeficiency disorders, except human immunodeficiency virus [HIV] diseaseInherited from D80-D89
- sarcoidosisInherited from D80-D89
Excludes 1
Official- autoimmune disease (systemic) NOS (M35.9)Inherited from D80-D89, D81
- functional disorders of polymorphonuclear neutrophils (D71-)Inherited from D80-D89, D81
- human immunodeficiency virus [HIV] disease (B20)Inherited from D80-D89, D81
- autosomal recessive agammaglobulinemia (Swiss type) (D80.0)Inherited from D80-D89, D81
Code First
OfficialNo Code First sequencing instructions are included in this display for D81.4. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for D81.4. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for D81.4. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is D81.4 an HCC code?
Yes. D81.4 (Nezelof's syndrome) maps to HCC 115, Specified Immunodeficiencies and White Blood Cell Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.565. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: D81.4 is billable and maps to V28 HCC 115, Specified Immunodeficiencies and White Blood Cell Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- D81.4
- Description
- Nezelof's syndrome
- HCC (V28)
- HCC 115 — Specified Immunodeficiencies and White Blood Cell Disorders
- RAF reference coefficient
- 0.565
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work D81.4 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for D81.4
For D81.4, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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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 source-labeled community, non-dual, aged reference coefficient of 0.565. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Confirm diagnosis through immunological testing showing T-cell lymphopenia with normal B-cells. For D81.4, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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).