Hydroxyprolinemia

IN a previous communication1 an eleven-year-old mentally retarded patient was reported to have persistent marked elevation of the unbound (free) hydroxyproline concentration in plasma and urine. At the time of that report the cause of the metabolic abnormality had not been determined.Evidence is presented below that this patient has an abnormality in the degradation of L-hydroxyproline, resulting in the accumulation of free hydroxyproline in the plasma with overflow into the urine. The deficient enzyme appears to be that which mediates the oxidation of L-hydroxyproline to Δ1-pyrroline-3-hydroxy-5-carboxylic acid; this is the first step in L-hydroxyproline degradation.Clinical DescriptionThe . . .