D81.7
BillableMajor histocompatibility complex class II deficiency
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D81.7 an HCC code?
Yes. D81.7 maps to Common Variable and Combined Immunodeficiencies 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 D81.7
For D81.7to 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 D81.7 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D81.7 is the ICD-10-CM diagnosis code for major histocompatibility complex class ii deficiency. A rare immune disorder where cells lack major histocompatibility complex class II proteins, which help coordinate immune responses and fight infections. D81.7 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, D81.7 maps to Common Variable and Combined Immunodeficiencies (HCC 114) with a community, non-dual, aged base RAF weight of 2.262. Under the older CMS-HCC V24 model, D81.7 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.
Distinguish from D81.6 (class I deficiency); class II deficiency typically presents with more severe infections and diarrhea. Because D81.7 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 D81.7 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Distinguish from D81.6 (class I deficiency); class II deficiency typically presents with more severe infections and diarrhea
- •Document associated opportunistic infections and autoimmune manifestations separately
Clinical Significance
Major histocompatibility complex class II deficiency, also known as bare lymphocyte syndrome type II, is a severe combined immunodeficiency where cells fail to express human leukocyte antigen class II molecules, preventing normal CD4+ T-cell development and thymic selection. This results in profound immune deficiency with early-onset severe infections, chronic diarrhea, and failure to thrive, typically presenting in the first year of life.
Documentation Requirements
- ✓Documentation must include flow cytometry showing absent human leukocyte antigen class II expression on antigen-presenting cells, CD4+ T-cell counts (severely reduced), immunoglobulin levels (typically low due to absent T-cell help), genetic testing identifying the specific transcription factor mutation (CIITA, RFX5, RFXAP, or RFXANK), and clinical course including infections and growth parameters.
Commonly Confused Codes
- •D81.6 (major histocompatibility complex class I deficiency, which is less severe and affects CD8+ cells), D81.1 (severe combined immunodeficiency with low T
- •and B-cells from other genetic causes), D81.0 (severe combined immunodeficiency with reticular dysgenesis which also affects myeloid cells), D81.9 (combined immunodeficiency, unspecified).