A very rare inherited metabolic disorder involving high levels of proline in the blood and urine due to a deficiency of the enzyme proline oxidase. There are two subtypes of the disorder with type II being more severe (higher blood levels of praline). Type I is generally asymptomatic wheras type II tends to involve neurological symptoms.


* Asymptomatic * Increased blood proline level * Increased urine hydroxyproline level * Increased urine glycine level * Neurological symptoms


Mutations in the ALDH4A1 and PRODH genes cause hyperprolinemia. Inherited hyperprolinemia is caused by deficiencies in the enzymes that break down (degrade) proline. Hyperprolinemia type I is caused by a mutation in the PRODH gene, which provides instructions for producing the enzyme proline oxidase. This enzyme begins the process of degrading proline by starting the reaction that converts it to pyrroline-5-carboxylate.