D55.21 ICD-10-CM Code: Anemia due to pyruvate kinase deficiency
HCC Buddy Code Card
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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) / Hemolytic anemias (D55-D59)
D55.21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceAnemia due to pyruvate kinase deficiency
A type of anemia caused by deficiency of the enzyme pyruvate kinase, which is needed for red blood cells to produce energy. This leads to premature destruction of red blood cells and anemia.
Buddy Insight
Pyruvate kinase deficiency is the most common cause of hereditary non-spherocytic hemolytic anemia and the most frequent glycolytic enzyme deficiency affecting red blood cells.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
MappedHCC 48
RAF 0.192
ACA/HHS
N/A—
Not mapped
ESRD/PACE
MappedHCC 48
RAF 0.063
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- PK deficiency anemia
- Pyruvate kinase deficiency anemia
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for D55.21 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for D55.21 in this effective period.
Excludes 1
Official- disorders of glycolysis not associated with anemia (E74.81-)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for D55.21 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for D55.21 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for D55.21 in this effective period.
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 D55.21 an HCC code?
Yes. D55.21 maps to Coagulation Defects and Other Specified Hematological Disorders under the V24 model but is not retained in V28.
- Code
- D55.21
- Description
- Anemia due to pyruvate kinase deficiency
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so 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 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.
Work D55.21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for D55.21
For D55.21 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 D55.21 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
D55.21 is the ICD-10-CM diagnosis code for anemia due to pyruvate kinase deficiency. A type of anemia caused by deficiency of the enzyme pyruvate kinase, which is needed for red blood cells to produce energy. This leads to premature destruction of red blood cells and anemia. D55.21 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 older CMS-HCC V24 model, D55.21 maps to Coagulation Defects and Other Specified Hematological Disorders (HCC 48) with a community, non-dual, aged base RAF weight of 0.192. 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.
Document severity and frequency of hemolytic episodes. Because D55.21 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 D55.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document severity and frequency of hemolytic episodes
- •Note any complications such as gallstones or splenomegaly that may result from chronic hemolysis
Clinical Significance
Pyruvate kinase deficiency is the most common cause of hereditary non-spherocytic hemolytic anemia and the most frequent glycolytic enzyme deficiency affecting red blood cells. It causes chronic hemolysis of variable severity, ranging from fully compensated anemia to transfusion-dependent disease. Complications include gallstones from chronic bilirubin turnover, iron overload from transfusions, and splenomegaly from extramedullary hematopoiesis.
Documentation Requirements
- ✓Document the confirmed diagnosis with pyruvate kinase enzyme activity assay or genetic testing results.
- ✓Record severity indicators including hemoglobin levels, reticulocyte count, transfusion frequency, and complications such as cholelithiasis, splenomegaly, or iron overload.
- ✓Note whether splenectomy has been performed and current management including folic acid supplementation and chelation therapy if applicable.
Commonly Confused Codes
- •D55.21 vs. D55.29 (Anemia due to other glycolytic enzyme disorders) -
- •use D55.21 specifically for pyruvate kinase deficiency, not for hexokinase or other glycolytic enzyme defects. D55.21 vs. D58.0 (Hereditary spherocytosis) -
- •pyruvate kinase deficiency causes non-spherocytic hemolytic anemia. D55.21 vs. D55.0 (Glucose-6-phosphate dehydrogenase deficiency) -
- •different metabolic pathway entirely.