D81.9 Combined immunodeficiency, unspecified

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

Applicable to

• Severe combined immunodeficiency disorder [SCID] NOS

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 D81.9

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 D81.9

• Agammaglobulinemia (acquired (secondary)) (nonfamilial) › with › lymphopenia
• Agammaglobulinemia (acquired (secondary)) (nonfamilial) › lymphopenic
• Deficiency, deficient › immunity › combined
• Immunodeficiency › combined
• Immunodeficiency › combined › severe (SCID)
• Immunodeficiency › severe combined (SCID)
• Syndrome › combined immunity deficiency
• Syndrome › immunity deficiency, combined
• Syndrome › immunodeficiency › combined

Nearby codes

• D81.810 Biotinidase deficiency
• D81.818 Other biotin-dependent carboxylase deficiency
• D81.819 Biotin-dependent carboxylase deficiency, unspecified
• D81.82 Activated Phosphoinositide 3-kinase Delta Syndrome [APDS]
• D81.89 Other combined immunodeficiencies
• D81.9 Combined immunodeficiency, unspecified (this code)