Alphabetic Index FY2027

D66

Hereditary factor VIII deficiency

FY2027Chapter 3: Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism/D65–D69 Coagulation defects, purpura and other hemorrhagic conditions

BillableComplete code, valid to report
Care settingsHome Health Primary · MMTA - Infectious Disease, Neoplasms, and Blood-Forming DiseasesHospital MCC

D66 is a billable ICD-10-CM diagnosis code for hereditary factor VIII deficiency. It is part of the FY2027 code set, effective October 1, 2026. The Alphabetic Index lists it under 11 entries. Its coding notes include 1 Excludes1 entry and 9 Excludes2 entries.

Excludes1

Not coded here. The listed conditions generally should not be reported together.

This code
  • factor VIII deficiency with vascular defect (D68.0-)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Also from chapter/block level (9 notes)
Inherited from Chapter 3 Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
  • autoimmune disease (systemic) NOS (M35.9)
  • certain conditions originating in the perinatal period (P00-P96)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • human immunodeficiency virus [HIV] disease (B20)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Home Health Primary

Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Infectious Disease, Neoplasms, and Blood-Forming Diseases clinical group.

Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026

Hospital MCC

Counts as a major complication or comorbidity (MCC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 51 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.

Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix C

Inclusion terms

Conditions classified to this code.

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

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 11 entries