描述
Purine nucleoside phosphorylase deficiency (Nucleoside phosphorylase; Immunodeficiency) is a rare disease causing severe immunodeficiency. The disease is caused by a mutation in the enzyme purine nucleoside phosphorylase. The enzyme is necessary for purine breakdown. The mutation causes deoxy-GTP (dGTP) to accumulate which causes T-cell toxicity. The disease results in accumulation of guanosine, inosine, and uric acid in serum; and orotic acid in some cases in the urine. Symptoms include anemia, ataxia, hypotonia, lymphopenia, mental retardation, and tremor or twitching.