What is ICD-10 code D81.0?

D81.0 is the ICD-10-CM diagnosis code for Severe combined immunodeficiency [SCID] with reticular dysgenesis. A severe inherited immune disorder where the body cannot develop infection-fighting cells and has abnormal bone marrow development. D81.0 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. D81.0 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. D81.0 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. D81.0 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.

Which HCC does D81.0 map to under V28?

D81.0 maps to CMS-HCC V28 HCC 114 (Common Variable and Combined Immunodeficiencies). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM D81.0: Severe combined

D81.0 maps to CMS-HCC V28 114. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupD81.0Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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)

D81.0

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Severe combined immunodeficiency [SCID] with reticular dysgenesis

A severe inherited immune disorder where the body cannot develop infection-fighting cells and has abnormal bone marrow development.

Buddy Insight

CMS-HCC V28

Mapped

HCC 114

Common Variable and Combined ...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 073

HHS-HCC 073 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 47

Disorders of Immunity

Code-level coefficient reference

RXHCC

Mapped

HCC 99

Immune Disorders

Code-level coefficient reference

Code Book Path

Official

D81Combined immunodeficiencies

D81.0Severe combined immunodeficiency [SCID] with reticular dysgenesis

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for D81.0 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for D81.0 in this effective period.

Related Child Codes

Official

D81.1Severe combined immunodeficiency [SCID] with low T- and B-cell numbers

D81.2Severe combined immunodeficiency [SCID] with low or normal B-cell numbers

D81.3Adenosine deaminase [ADA] deficiency

D81.4Nezelof's syndrome

D81.5Purine nucleoside phosphorylase [PNP] deficiency

Includes

Official

ICD-10-CM does not list Includes notes for D81.0 in this effective period.

Excludes 1

Official

autosomal recessive agammaglobulinemia (Swiss type) (D80.0)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for D81.0 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for D81.0 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for D81.0 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation must include evidence of absent T-cells, B-cells, and natural killer cells, severe neutropenia/agranulocytosis confirming the myeloid defect, bone marrow biopsy showing reticular dysgenesis, genetic testing results when available, and treatment plan including hematopoietic stem cell transplantation.

Document the neonatal presentation and severity of clinical course.

MEAT Support

HCC Buddy guidance

Document the neonatal presentation and severity of clinical course.

Audit Caution

HCC Buddy guidance

Reticular dysgenesis is distinguished from other SCID variants by the additional myeloid lineage failure

if neutrophil counts are normal, this code is incorrect. Do not confuse with other forms of SCID that spare the myeloid compartment. This condition is identified through newborn screening in many states, making early and accurate coding essential for care coordination.

Common Mistakes

HCC Buddy guidance

D81.1 (severe combined immunodeficiency with low T

and B-cell numbers, which preserves myeloid cells), D81.2 (severe combined immunodeficiency with low or normal B-cell numbers), D81.9 (combined immunodeficiency, unspecified, which lacks the reticular dysgenesis component), D70.0 (congenital agranulocytosis, which affects only neutrophils without the lymphoid deficiency).

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 D81.0 an HCC code?

Yes. D81.0 (Severe combined immunodeficiency [SCID] with reticular dysgenesis) maps to HCC 114, Common Variable and Combined Immunodeficiencies under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 2.262. 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: D81.0 is billable and maps to V28 HCC 114, Common Variable and Combined Immunodeficiencies. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: D81.0
Description: Severe combined immunodeficiency [SCID] with reticular dysgenesis
HCC (V28): HCC 114 — Common Variable and Combined Immunodeficiencies
RAF reference coefficient: 2.262
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 114, Common Variable and Combined Immunodeficiencies

2.262

ESRDHCC 47, Disorders of Immunity

Not separately weighted

RxHCCHCC 99, Immune Disorders

Not separately weighted

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 D81.0 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for D81.0

For D81.0 to 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 D81.0 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

D81.0 is the ICD-10-CM diagnosis code for severe combined immunodeficiency [scid] with reticular dysgenesis. A severe inherited immune disorder where the body cannot develop infection-fighting cells and has abnormal bone marrow development. D81.0 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, D81.0 maps to Common Variable and Combined Immunodeficiencies (HCC 114) with a source-labeled community, non-dual, aged reference coefficient of 2.262. No V24 mapping is shown for D81.0; use the applicable model and payment year when reviewing the V28 mapping. 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. 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.

This is a life-threatening condition requiring immediate documentation of reticular dysgenesis confirmation. Because D81.0 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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 D81.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is a life-threatening condition requiring immediate documentation of reticular dysgenesis confirmation
•Verify genetic testing results are documented to support diagnosis

Clinical Significance

Severe combined immunodeficiency with reticular dysgenesis is the most severe form of SCID, characterized by complete absence of both lymphoid and myeloid cell lineages due to a defect in mitochondrial adenylate kinase 2. This uniformly fatal condition without treatment presents in the neonatal period with profound pancytopenia, absent thymus, and extreme vulnerability to all types of infections.

Documentation Requirements

✓Documentation must include evidence of absent T-cells, B-cells, and natural killer cells, severe neutropenia/agranulocytosis confirming the myeloid defect, bone marrow biopsy showing reticular dysgenesis, genetic testing results when available, and treatment plan including hematopoietic stem cell transplantation.
✓Document the neonatal presentation and severity of clinical course.

Commonly Confused Codes

•D81.1 (severe combined immunodeficiency with low T
•and B-cell numbers, which preserves myeloid cells), D81.2 (severe combined immunodeficiency with low or normal B-cell numbers), D81.9 (combined immunodeficiency, unspecified, which lacks the reticular dysgenesis component), D70.0 (congenital agranulocytosis, which affects only neutrophils without the lymphoid deficiency).