2026 ICD-10-CM Diagnosis Code D66Hereditary factor VIII deficiency

ICD-10-CM Codes›D50–D89›D65-D69›D66

ICD-10-CM D66
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D66 is a billable ICD-10-CM diagnosis code for hereditary factor VIII deficiency. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 813. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 50 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Coagulation and hemorrhagic disorders.

For Medicare Advantage risk adjustment, D66 maps to CMS-HCC Category 111 (Hemophilia, Male) under the V28 model, adding a risk factor of about 4.639 for a community, non-dual, aged beneficiary in payment year 2026.

Code Identity

ICD-10-CM Code
D66
Billable Status
Yes — Valid for Submission
Code Describes
Hereditary factor VIII deficiency
Short Description
Hereditary factor VIII deficiency
Same as the full description in the CMS dataset.
Chapter
D65-D69
Coagulation defects, purpura and other hemorrhagic conditions

Code Classification

ChapterD50–D89Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
SectionD65-D69Coagulation defects, purpura and other hemorrhagic conditions
CategoryD66Hereditary factor VIII deficiency
This CodeD66Hereditary factor VIII deficiency

Medicare Risk Adjustment (HCC)Billing

D66 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.

CMS-HCC V28 Category (Payment Model)
HCC 111— Hemophilia, Male
Payment HCC · PY 2026 one of 2 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+4.639
community, non-dual, aged · ranges 4.639–32.199 across segments
Hierarchy
Supersedes HCC 112
less severe related categories are not paid alongside HCC 111
Prior Model (CMS-HCC V24)
HCC 46
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 46 · ESRD (V21): HCC 46 · ESRD (V24): HCC 46
ESRD V21 weights: 0.180 dialysis, 0.766–1.325 functioning graft · ESRD V24 weights: 0.223 dialysis, 0.748–4.064 functioning graft
Part D (RxHCC)
Not mapped
D66 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Combined deficiency of factor V and factor VIII
  • Factor V deficiency
  • Factor VIII deficiency
  • Hemophilia
  • Hemophilic arthropathy of bilateral ankles
  • Hemophilic arthropathy of bilateral elbows
  • Hemophilic arthropathy of bilateral hips
  • Hemophilic arthropathy of bilateral knees
  • Hemophilic arthropathy of bilateral shoulders
  • Hemophilic arthropathy of bilateral wrists
  • Hemophilic arthropathy of left ankle
  • Hemophilic arthropathy of left elbow
  • Hemophilic arthropathy of left hip
  • Hemophilic arthropathy of left knee
  • Hemophilic arthropathy of left shoulder
  • Hemophilic arthropathy of left wrist
  • Hemophilic arthropathy of right ankle
  • Hemophilic arthropathy of right elbow
  • Hemophilic arthropathy of right hip
  • Hemophilic arthropathy of right knee
  • Hemophilic arthropathy of right shoulder
  • Hemophilic arthropathy of right wrist
  • Hereditary combined coagulation factor deficiency
  • Hereditary factor VIII deficiency disease
  • Hereditary factor VIII deficiency disease with inhibitor
  • Hereditary factor VIII deficiency disease without inhibitor
  • Lamellar ichthyosis
  • Mild hereditary factor VIII deficiency disease
  • Mild hereditary factor VIII deficiency disease with high response inhibitor
  • Mild hereditary factor VIII deficiency disease with inhibitor
  • Mild hereditary factor VIII deficiency disease with low response inhibitor
  • Mild hereditary factor VIII deficiency disease without inhibitor
  • Moderate hereditary factor VIII deficiency disease
  • Moderate hereditary factor VIII deficiency disease with high response inhibitor
  • Moderate hereditary factor VIII deficiency disease with inhibitor
  • Moderate hereditary factor VIII deficiency disease with low response inhibitor
  • Moderate hereditary factor VIII deficiency disease without inhibitor
  • Multiple sclerosis, ichthyosis, factor VIII deficiency syndrome
  • Severe hereditary factor VIII deficiency disease
  • Severe hereditary factor VIII deficiency disease with high response inhibitor
  • Severe hereditary factor VIII deficiency disease with inhibitor
  • Severe hereditary factor VIII deficiency disease with low response inhibitor
  • Severe hereditary factor VIII deficiency disease without inhibitor

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Classical hemophilia
  • Deficiency factor VIII (with functional defect)
  • Hemophilia NOS
  • Hemophilia A

Type 1 Excludes

  • factor VIII deficiency with vascular defect D68.0

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR BLD006
Coagulation and hemorrhagic disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Factor V Deficiency

    a deficiency of blood coagulation factor v (known as proaccelerin or accelerator globulin or labile factor) leading to a rare hemorrhagic tendency known as owren's disease or parahemophilia. it varies greatly in severity. factor v deficiency is an autosomal recessive trait. (dorland, 27th ed)

  • ABCA12 wt Allele|ABC12|ARCI4A|ARCI4B|ATP Binding Cassette Subfamily A Member 12 wt Allele|ATP-Binding Cassette, Sub-Family A (ABC1), Member 12 Gene|ATP-Binding Cassette, Subfamily A, Member 12 Gene|DKFZP434G232|ICR2B|Ichthyosis Congenita II, Lamellar Ichthyosis B Gene|LI2

    human abca12 wild-type allele is located in the vicinity of 2q35 and is approximately 207 kb in length. this allele, which encodes glucosylceramide transporter abca12 protein, plays a role in both the membrane localization of glucosylceramide and other lipids in lamellar granules and in cholesterol transport. mutation of the gene is associated with autosomal recessive congenital ichthyosis (arci) types 4a and 4b (harlequin).

  • Lamellar Ichthyosis

    a very rare, autosomal recessive inherited skin disorder present at birth. it is characterized by the presence of a transparent membrane encasing the newborn. this membrane sheds in about two weeks after birth to reveal generalized scaling and skin erythema.

  • Acquired Factor V Deficiency

    an acquired coagulation disorder characterized by the partial or complete absence of factor v activity in the blood.

  • Factor V Deficiency

    a coagulation disorder characterized by the partial or complete absence of factor v activity in the blood.

  • Hereditary Factor V Deficiency|Owren Disease

    a very rare autosomal recessive inherited blood coagulation disorder characterized by deficiency of factor v, resulting in bleeding.

Patient EducationClinical

Hemophilia

Hemophilia is a rare bleeding disorder in which the blood does not clot properly. This can lead to problems with bleeding too much after an injury or surgery. You can also have sudden bleeding inside your body, such as in your joints, muscles, and organs.

The full article covers:

  • What is hemophilia?
  • What are the types of hemophilia?
  • What causes hemophilia?
  • Who is at risk for hemophilia?
  • What are the symptoms of hemophilia?
  • How is hemophilia diagnosed?
  • What are the treatments for hemophilia?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert D66 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
286.0 Cong factor viii diord
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About D66Overview

What is the ICD-10 code for hereditary factor VIII deficiency?

The ICD-10-CM code for hereditary factor VIII deficiency is D66. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is D66 (Hereditary factor VIII deficiency) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hereditary factor VIII deficiency on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does D66 group to?

When hereditary factor VIII deficiency is the principal diagnosis on an inpatient stay, it groups to MS-DRG 813 (coagulation Disorders), which carries a relative weight of 1.5253. Higher weights mean higher Medicare reimbursement.

Is D66 a CC or MCC?

CMS lists D66 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 50 closely related codes in its exclusion list.

What is the ICD-9 equivalent of D66?

Under the General Equivalence Mappings, hereditary factor VIII deficiency converts to ICD-9-CM 286.0 (cong factor viii diord). The mapping is a direct match.

What HCC is D66?

D66 (hereditary factor VIII deficiency) maps to CMS-HCC Category 111 (Hemophilia, Male), commonly written as HCC 111, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 46 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.

Does D66 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, D66 adds a risk adjustment factor of about 4.639 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 4.639 to 32.199 depending on the payment segment). HCC 111 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 111 category page.