<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by phosphoribosylpyrophosphate synthetase superactivity ? [/INST] PRS superactivity is believed to be a rare disorder. Approximately 30 families with the condition have been reported. More than two thirds of these families are affected by the milder form of the disease. </s>