D80.5
BillableImmunodeficiency with increased immunoglobulin M [IgM]
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D80.5 an HCC code?
Yes. D80.5 maps to Disorders of Immunity, Neutropenia 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 D80.5
For D80.5to 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 D80.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D80.5 is the ICD-10-CM diagnosis code for immunodeficiency with increased immunoglobulin m [igm]. A condition where the body has abnormally high levels of IgM antibodies combined with deficiency of other antibody types. D80.5 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, D80.5 maps to Disorders of Immunity, Neutropenia (HCC 115) with a community, non-dual, aged base RAF weight of 0.369. Under the older CMS-HCC V24 model, D80.5 maps to Disorders of Immunity (HCC 47) with a community, non-dual, aged base RAF weight of 0.472. 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.
This represents a specific immunodeficiency pattern with elevated IgM; document other deficient immunoglobulins. Because D80.5 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 D80.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This represents a specific immunodeficiency pattern with elevated IgM; document other deficient immunoglobulins
- •Note any associated infections, autoimmune features, or lymphoid hyperplasia
Clinical Significance
Immunodeficiency with increased immunoglobulin M, also known as hyper-Immunoglobulin M syndrome, is a primary immunodeficiency caused by defective immunoglobulin class switching, resulting in elevated Immunoglobulin M but severely deficient Immunoglobulin G and Immunoglobulin A. Patients are highly susceptible to opportunistic infections including Pneumocystis jirovecii pneumonia, Cryptosporidium enteritis, and recurrent bacterial infections.
Documentation Requirements
- ✓Documentation must include quantitative immunoglobulin levels showing elevated Immunoglobulin M with reduced Immunoglobulin G and Immunoglobulin A, genetic testing results if available (CD40 ligand or activation-induced cytidine deaminase mutations), clinical manifestations including infection history, neutropenia if present, and treatment including immunoglobulin replacement therapy and prophylactic antimicrobials.
Commonly Confused Codes
- •D80.4 (selective Immunoglobulin M deficiency which has LOW Immunoglobulin M, the opposite pattern), D80.0 (hereditary hypogammaglobulinemia which has all immunoglobulins low), D81.2 (severe combined immunodeficiency with B-cell numbers preserved but different mechanism), D83.0 (common variable immunodeficiency with B-cell abnormalities, a different entity).