ICD-10 Code D81.5 – Purine nucleoside phosphorylase [PNP] deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D81.5 – Purine nucleoside phosphorylase [PNP] deficiency
What it is
D81.5 identifies purine nucleoside phosphorylase deficiency, a rare inherited immunodeficiency. It affects immune cell function and can lead to severe, lifelong susceptibility to infections.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include recurrent or severe infections, lymphopenia, and impaired T-cell function. Some patients also have neurologic or autoimmune features.
When to use this code
Use D81.5 when the provider documents PNP deficiency, purine nucleoside phosphorylase deficiency, or an equivalent confirmed diagnosis. Apply it for encounters focused on this specific inherited immunodeficiency, even if the visit is for evaluation, follow-up, or complication review.
Do not use it for nonspecific immune problems without confirmation. Check documentation if the chart only notes recurrent infections, combined immunodeficiency, or suspected metabolic disease.
Do not use for
Do not assign this code for general immunodeficiency, transient low lymphocyte counts, or other combined immunodeficiency disorders. If PNP deficiency is not documented, check documentation.
Coding tip
Code D81.5 only when the diagnosis is explicit in the record; do not infer it from symptoms or genetic testing alone unless the provider confirms the condition.