What is ICD-10 code D56.4?

D56.4 is the ICD-10-CM diagnosis code for Hereditary persistence of fetal hemoglobin [HPFH]. A rare genetic condition where a person continues to produce fetal hemoglobin into adulthood instead of switching to adult hemoglobin. This is usually benign and causes little to no health problems. D56.4 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. D56.4 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. D56.4 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. D56.4 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.

What is the V28 vs V24 difference for D56.4?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. D56.4 was a payment HCC under V24 (Coagulation Defects and Other Specified Hematological Disorders) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting D56.4?

HPFH is typically a benign finding discovered incidentally on hemoglobin electrophoresis Document whether this is causing any clinical symptoms or complications Because D56.4 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM D56.4: Hereditary persistence

ICD-10-CM Code View

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Code lookupD56.4Effective 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) / Hemolytic anemias (D55-D59)

D56.4

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

Hereditary persistence of fetal hemoglobin [HPFH]

A rare genetic condition where a person continues to produce fetal hemoglobin into adulthood instead of switching to adult hemoglobin. This is usually benign and causes little to no health problems.

Buddy Insight

Hereditary persistence of fetal hemoglobin is a benign genetic condition where fetal hemoglobin production continues into adulthood at elevated levels instead of being silenced after infancy.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 48

Coagulation Defects and Other...

RAF 0.192

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 48

Coagulation Defects and Other...

RAF 0.063

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

D56Thalassemia

D56.4Hereditary persistence of fetal hemoglobin [HPFH]

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for D56.4 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for D56.4 in this effective period.

Related Child Codes

Official

D56.0Alpha thalassemia

D56.1Beta thalassemia

D56.2Delta-beta thalassemia

D56.3Thalassemia minor

D56.5Hemoglobin E-beta thalassemia

Includes

Official

ICD-10-CM does not list Includes notes for D56.4 in this effective period.

Excludes 1

Official

sickle-cell thalassemia (D57.4-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for D56.4 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for D56.4 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for D56.4 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation should include hemoglobin electrophoresis results showing elevated fetal hemoglobin levels (typically 15-30% in heterozygotes, near 100% in homozygotes), normal or near-normal hemoglobin and mean corpuscular volume, and absence of significant anemia or hemolysis.

Genetic testing results should be recorded if available.

Document that the condition is clinically benign and does not require treatment, and note its relevance for genetic counseling.

MEAT Support

HCC Buddy guidance

Genetic testing results should be recorded if available.

Document that the condition is clinically benign and does not require treatment, and note its relevance for genetic counseling.

Audit Caution

HCC Buddy guidance

This code has no V28 HCC mapping, so it provides no risk adjustment value under the new model. Because hereditary persistence of fetal hemoglobin is typically a benign incidental finding, providers may not document it at encounters, making recapture difficult. Ensure this is not confused with delta-beta thalassemia (D56.2), which does map to V28 HCC

The clinical distinction requires careful review of hemoglobin electrophoresis and complete blood count.

Common Mistakes

HCC Buddy guidance

D56.4 vs. D56.2 (Delta-beta thalassemia) -

both show elevated fetal hemoglobin, but delta-beta thalassemia causes anemia due to unbalanced globin chain production, while hereditary persistence of fetal hemoglobin has balanced production and minimal clinical impact. D56.4 vs. D56.1 (Beta thalassemia) -

beta thalassemia causes significant anemia. D56.4 vs. D56.9 (Thalassemia, unspecified) -

do not code hereditary persistence of fetal hemoglobin as unspecified thalassemia.

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is D56.4 an HCC code?

Yes. D56.4 maps to Coagulation Defects and Other Specified Hematological Disorders under the V24 model but is not retained in V28.

Code: D56.4
Description: Hereditary persistence of fetal hemoglobin [HPFH]
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 48, Coagulation Defects and Other Specified Hematological Disorders

0.192

ESRDHCC 48, Coagulation Defects and Other Specified Hematological Disorders

0.063

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 D56.4 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for D56.4

For D56.4to 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 D56.4 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

D56.4 is the ICD-10-CM diagnosis code for hereditary persistence of fetal hemoglobin [hpfh]. A rare genetic condition where a person continues to produce fetal hemoglobin into adulthood instead of switching to adult hemoglobin. This is usually benign and causes little to no health problems. D56.4 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, D56.4 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.

HPFH is typically a benign finding discovered incidentally on hemoglobin electrophoresis. Because D56.4 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 D56.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•HPFH is typically a benign finding discovered incidentally on hemoglobin electrophoresis
•Document whether this is causing any clinical symptoms or complications

Clinical Significance

Hereditary persistence of fetal hemoglobin is a benign genetic condition where fetal hemoglobin production continues into adulthood at elevated levels instead of being silenced after infancy. Unlike thalassemia syndromes, globin chain production is balanced, so there is no significant anemia or hemolysis. This condition is most commonly discovered incidentally on hemoglobin electrophoresis and is clinically important primarily for genetic counseling and distinguishing from pathologic hemoglobin disorders.

Documentation Requirements

✓Documentation should include hemoglobin electrophoresis results showing elevated fetal hemoglobin levels (typically 15-30% in heterozygotes, near 100% in homozygotes), normal or near-normal hemoglobin and mean corpuscular volume, and absence of significant anemia or hemolysis.
✓Genetic testing results should be recorded if available.
✓Document that the condition is clinically benign and does not require treatment, and note its relevance for genetic counseling.

Commonly Confused Codes

•D56.4 vs. D56.2 (Delta-beta thalassemia) -
•both show elevated fetal hemoglobin, but delta-beta thalassemia causes anemia due to unbalanced globin chain production, while hereditary persistence of fetal hemoglobin has balanced production and minimal clinical impact. D56.4 vs. D56.1 (Beta thalassemia) -
•beta thalassemia causes significant anemia. D56.4 vs. D56.9 (Thalassemia, unspecified) -
•do not code hereditary persistence of fetal hemoglobin as unspecified thalassemia.