Hypouricemia - the simple key towards diagnosis in a case of purine nucleoside phosphorylase deficiency, a rare and severe disease /Hipouricemia - cheia către diagnosticul unui caz de deficit de purin nucleozid fosforilază, o boală rară si severă

We describe the case of a 15 month old boy, investigated for repeated and prolonged infections, associated to progressive neurological impairment. Immunological work-up found low immunoglobulin levels and decreased numbers of T and B lymphocytes, with a T-B-NK+ phenotype. Imaging showed lack of thymus and cerebral cortex atrophy. The key towards the diagnosis was plasma uric acid determination: hypouricemia suggested purine nucleoside phosphorylase deficiency, a very rare disease, with only 67 reported cases worldwide. Diagnosis was confirmed by enzyme activity measured using a radioisotopic method.