PREPL in Health and Disease

PREPL is defective in hypotonia cystinuria syndrome and in isolated PREPL deficiency. The investigators have constructed a blood test to evaluate PREPL activity in patients with possible PREPL deficiency. The study will determine normal values for age (0-18) for PREPL activity in blood. Also, patients with a clinical phenotype that overlaps with PREPL deficiency (including patients with known primary PREPL deficiency and Prader-Willi syndrome) will be evaluated for PREPL activity in blood. A last part of the study will involve muscle biopsies during elective anesthesia/surgery for other reasons. There will be 2 groups: patients without signs of PREPL deficiency undergoing surgery (controls) and patients with Prader-Willi syndrome undergoing anesthesia or surgery (patients). The control group will be age-matched to the hypotonia group. In the muscle biopsies, PREPL activity and expression will be evaluated.