Purine nucleoside phosphorylase [PNP] deficiency

This code represents a rare, inherited immunodeficiency disorder characterized by a defect in the purine nucleoside phosphorylase enzyme. This enzyme deficiency leads to the accumulation of toxic purine metabolites, primarily affecting T-lymphocyte function and resulting in severe cellular immunodeficiency. Patients typically present with recurrent infections, neurological problems, and autoimmune manifestations.

Use this code for patients definitively diagnosed with purine nucleoside phosphorylase deficiency, often confirmed through enzyme assay or genetic testing. Documentation should clearly indicate the diagnosis of PNP deficiency as the underlying cause of the patient's immunodeficiency. This code is appropriate for both initial diagnosis and subsequent encounters related to managing the condition.

• Ensure documentation specifies "purine nucleoside phosphorylase" deficiency to differentiate from other immunodeficiencies.
• Code any associated manifestations, such as recurrent infections (e.g., B20-B99), neurological complications (e.g., G00-G99), or autoimmune disorders (e.g., M00-M99), as secondary diagnoses.
• Review genetic testing results or enzyme assay reports when available to support the diagnosis.