ICD-10 Code D81.31 – Severe combined immunodeficiency due to adenosine deaminase deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D81.31 – Severe combined immunodeficiency due to adenosine deaminase deficiency
What it is
D81.31 identifies severe combined immunodeficiency caused by adenosine deaminase deficiency. This is a rare inherited disorder that impairs T-cell, B-cell, and often natural killer cell function, leaving the patient highly vulnerable to infection.
Clinical signs
Clinical features vary; refer to documentation. Common findings include recurrent, severe, or opportunistic infections, poor growth, chronic diarrhea, and persistent lymphopenia. Diagnosis is usually supported by immunologic testing and genetic or enzyme studies.
When to use this code
Use this code when the provider documents severe combined immunodeficiency specifically due to adenosine deaminase deficiency. It is appropriate for confirmed hereditary immunodeficiency cases, including newborn screening follow-up or established diagnosis in specialty care. Check documentation if the cause is not stated.
Do not use for
Do not use this code for other forms of SCID, nonspecific immunodeficiency, or suspected disease without confirmation. If the record does not link the condition to adenosine deaminase deficiency, choose the more accurate documented diagnosis.
Coding tip
Code the documented etiology only when the provider clearly states ADA deficiency as the cause of SCID.