ICD-10 Code D81.6 – Major histocompatibility complex class I deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D81.6 – Major histocompatibility complex class I deficiency
What it is
D81.6 identifies major histocompatibility complex class I deficiency, a rare inherited immune disorder that affects how cells present antigens to the immune system. Use it when documentation specifically confirms this diagnosis.
Clinical signs
Clinical features vary; refer to documentation. Reported findings may include recurrent infections, chronic respiratory disease, and immune dysfunction consistent with impaired class I antigen presentation.
When to use this code
Use this code when the provider documents major histocompatibility complex class I deficiency, including confirmed genetic or immunologic evaluation. It may also apply when the diagnosis is stated in the assessment or discharge summary and is being managed or monitored.
Do not assign it for nonspecific recurrent infections alone. If the record only suggests an immune defect without confirmation, check documentation before coding.
Do not use for
Do not use D81.6 for general immunodeficiency, antibody deficiency, or other combined immune disorders unless the class I deficiency is explicitly documented. Check documentation if the condition is only suspected.
Coding tip
Code D81.6 only when the chart names this rare deficiency clearly; otherwise, query for the exact immune diagnosis.