ICD-10 Code D81.7 – Major histocompatibility complex class II deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D81.7 – Major histocompatibility complex class II deficiency
What it is
D81.7 identifies major histocompatibility complex class II deficiency, a rare inherited immunodeficiency. It means the body cannot properly express MHC class II molecules, which are needed for normal immune signaling.
Clinical signs
Clinical features vary; refer to documentation. Commonly documented findings include recurrent or severe infections, chronic diarrhea, failure to thrive, and marked susceptibility to opportunistic infections.
When to use this code
Use D81.7 when the clinician documents confirmed MHC class II deficiency or a diagnosis clearly equivalent to it. Code it for inherited immunodeficiency cases supported by specialist evaluation, genetic testing, or established immunology workup. Do not code from suspicion alone unless documentation states the condition as diagnosed.
Do not use for
Do not use this code for nonspecific immune deficiency, transient low immunity, or recurrent infection without a documented MHC class II defect. Check documentation if the record only mentions abnormal immune testing.
Coding tip
Verify that the chart names the disorder specifically; vague terms such as “immunodeficiency” usually need a different code.