Long-Term Evolution of Type 1 Adenine Phosphoribosyltransferase (APRT) Deficiency

Abstract

There are two types of inherited adenine phosphoribosyltransferase (APRT) deficiency: type I (APRT*Qo) in which enzyme activity is practically undetectable and which is seen predominantly in Caucasians, and type II (APRT*J) in which there is a partial deficiency of the enzyme and which, until now, has been found only in the Japanese. Most studies on clinical, biochemical and therapeutic aspects have been performed in type I APRT deficiency. From these studies it has become apparent that the only abnormality in these patients is the formation of 2,8.dihydroxyadenine (2,8 DHA) crystals in the urinary tract. It is their presence in the urinary tract and their possible accretion to stones which determines the clinical symptomatology and, through damage to the kidney, the prognosis. Treatment, therefore, is aimed at preventing 2,8.DHA stone formation: this may be obtained by measures such as forced diuresis and dietary purine restriction but in some patients treatment with allopurinol (AP) may be necessary.