Purine-Nucleoside Phosphorylase Deficiency

**Semantic type:** Disease or Syndrome

**Definition:** PNP reversibly catalyzes the phosphorolysis of the purine nucleosides, (deoxy)inosine and (deoxy)guanosine, to their respective purine bases and the corresponding ribose-1-phosphate. Deficiency in this enzyme is an autosomal recessive cause of combined immunodeficiency.