Purine nucleoside phosphorylase deficiency is an autosomal recessive inherited disorder that interrupts both the catabolism of inosine into hypoxanthine and guanosine into guanine, and leads to the accumulation of guanosine, inosine, and their deoxified byproducts. As a result levels of guanine, hypoxanthine, xanthine and uric acid are depressed. The main clinical presentation is recurrent infections. Symptoms usually occur towards the end of the patient's second year and persist during the 5th or 6th first years. Children are particularly prone to viral infections (chicken pox, mumps, cytomegalovirus) and vaccines, but suppurant bacterial infections have also been noted. One third of all patients have anemia, 2/3 have neurological signs (ataxia, spastic tetraplegy and tremor). Severe immune deficiency is usually found, affecting cell immunity and causing markedly low levels of T-cells. Diagnosis is suggested by T-cell deficiency combined with severe hypouricemia, and confirmed by measuring enzymatic deficiency in red blood cells. The disease is spontaneously severe. Patients are treated symptomatically and preventively for infections, but bone marrow transplantation and repeated irradiated blood transfusions are the only real treatments. Antenatal diagnosis is feasible.
Last update: March 2004