D59.5
BillableParoxysmal nocturnal hemoglobinuria [Marchiafava-Micheli]
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D59.5 an HCC code?
Yes. D59.5 maps to Hemolytic and Aplastic Anemias under the CMS-HCC V28 risk adjustment model (and Severe Hematological Disorders 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 D59.5
For D59.5 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 D59.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D59.5 is the ICD-10-CM diagnosis code for paroxysmal nocturnal hemoglobinuria [marchiafava-micheli]. A rare blood disorder where red blood cells are destroyed in the bloodstream, particularly at night, leading to anemia and dark urine. D59.5 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 hemolytic anemias (d55-d59).
Under the CMS-HCC V28 risk adjustment model, D59.5 maps to Hemolytic and Aplastic Anemias (HCC 109) with a community, non-dual, aged base RAF weight of 0.291. Under the older CMS-HCC V24 model, D59.5 maps to Severe Hematological Disorders (HCC 46) with a community, non-dual, aged base RAF weight of 0.666. 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 is a specific named condition (Marchiafava-Micheli disease); document any hemoglobinuria or thrombotic complications. Because D59.5 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 D59.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a specific named condition (Marchiafava-Micheli disease); document any hemoglobinuria or thrombotic complications
- •Note any treatment with complement inhibitors or anticoagulation therapy
Clinical Significance
Paroxysmal nocturnal hemoglobinuria (Marchiafava-Micheli disease) is a rare acquired clonal stem cell disorder caused by somatic mutations in the PIGA gene, resulting in deficiency of glycosylphosphatidylinositol-anchored complement regulatory proteins (CD55 and CD59) on blood cell surfaces. This leaves red blood cells vulnerable to complement-mediated lysis, particularly during sleep when mild respiratory acidosis enhances complement activation. The disease triad includes intravascular hemolysis, bone marrow failure, and a strong predisposition to venous thrombosis, which is the leading cause of death.
Documentation Requirements
- ✓Document flow cytometry results showing deficiency of CD55 and CD59 (glycosylphosphatidylinositol-anchored proteins) on red blood cells and granulocytes.
- ✓Record hemoglobin levels, lactate dehydrogenase (often markedly elevated), reticulocyte count, haptoglobin (typically undetectable), and urinalysis showing hemoglobinuria.
- ✓Document any thrombotic events (Budd-Chiari syndrome, cerebral vein thrombosis, portal vein thrombosis).
- ✓Include treatment with complement inhibitors (eculizumab, ravulizumab) and anticoagulation status.
Excludes 1 — Do NOT code together
- hemoglobinuria NOS (R82.3)
Commonly Confused Codes
- •D59.6 (Hemoglobinuria due to hemolysis from other external causes) involves external triggers rather than intrinsic complement susceptibility.
- •D61.x (Aplastic anemia) may coexist, as paroxysmal nocturnal hemoglobinuria clones frequently arise from aplastic bone marrow.
- •D59.10-D59.19 (Autoimmune hemolytic anemias) involve antibody-mediated rather than complement-mediated hemolysis.
- •D68.x (Coagulation disorders) may be coded additionally for thrombotic complications.