D81.6 Major histocompatibility complex class I deficiency

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• Bare lymphocyte syndrome

Applies from D81 Combined immunodeficiencies

Excludes1 (never code together)

• autosomal recessive agammaglobulinemia (Swiss type) (D80.0)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 114 — Common Variable and Combined Immunodeficiencies
• CMS-HCC V22: HCC 47 — Disorders of Immunity
• RxHCC V08: HCC 99 — Immune Disorders
• ESRD V24: HCC 47

MS-DRG index

Defines the logic of DRG(s) 808-810 in MDC 16.

Approximate ICD-9-CM (GEMs)

• 279.2 Combined immunity deficiency (approximate)

Code annotations containing back-references to D81.6

Back-references to D81

• Type 1 Excludes: D72 Other disorders of white blood cells ("immunity disorders (D80-D89)")
• Type 1 Excludes: D84.81 Immunodeficiency due to conditions classified elsewhere ("certain disorders involving the immune mechanism (D80-D83, D84.0, D84.1, D84.9)")
• Type 1 Excludes: E79 Disorders of purine and pyrimidine metabolism ("combined immunodeficiency disorders (D81.-)")

Diagnosis Index entries for D81.6

• Deficiency, deficient › major histocompatibility complex › class I
• Syndrome › bare lymphocyte

Nearby codes

• D81.31 Severe combined immunodeficiency due to adenosine deaminase deficiency
• D81.32 Adenosine deaminase 2 deficiency
• D81.39 Other adenosine deaminase deficiency
• D81.4 Nezelof's syndrome
• D81.5 Purine nucleoside phosphorylase [PNP] deficiency
• D81.6 Major histocompatibility complex class I deficiency (this code)
• D81.7 Major histocompatibility complex class II deficiency
• D81.8 Other combined immunodeficiencies
• D81.81 Biotin-dependent carboxylase deficiency
• D81.810 Biotinidase deficiency
• D81.818 Other biotin-dependent carboxylase deficiency