Hyperprolinemia is a condition which occurs when the amino acid proline is not broken down properly by the enzymes proline oxidase or pyrroline-5-carboxylate dehydrogenase, causing a buildup of proline in the body. Genetics Mutations in the ALDH4A1 and PRODH genes cause hyperprolinemia.Hyperprolinemia type I is caused by a mutation in the PRODH gene, which codes for the enzyme proline oxidase. [Source: Wikipedia ]