Association of hyperprolinaemia type I and heparin cofactor II deficiency with CATCH 22 syndrome: evidence for a contiguous gene syndrome locating the proline oxidase gene

Summary Increased proline levels were found in plasma of a girl with slight psychomotor retardation, epilepsy, obesity, scoliosis, hypocalcaemia, variable lymphocytopenia and facial dysmorphy suggestive of CATCH 22 syndrome. Fluorescence in situ hybridization indicated the presence of a submicroscopic 22q11 deletion, confirming this diagnosis. Further investigation showed evidence that the patient was heterozygous for heparin cofactor II deficiency and for hyperprolinaemia type I, a proline catabolic disorder due to proline oxidase deficiency. This association extends the CATCH 22 syndrome and suggests that expression of the proline oxidase gene depends on the chromosome 22q11 region.