Hyperprolinemia is an excess of a particular protein building block (amino acid), called proline, in the blood. This condition generally occurs when proline is not broken down properly by the body. There are two forms of hyperprolinemia, called type I and type II.

Hyperprolinemia is caused by variants (also known as mutations) in the ALDH4A1 and PRODH genes. These genes provide instructions for enzymes that break down proline.

It is difficult to determine the prevalence of hyperprolinemia type I because most people with the condition do not have any symptoms. Hyperprolinemia type II is thought to be a rare condition; its prevalence is also unknown.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have variants. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but do not show signs and symptoms of the condition. In about one-third of cases, individuals carrying one copy of an altered PRODH gene have moderately elevated levels of proline in their blood, but these levels do not cause any health problems. Individuals with one altered ALDH4A1 gene have normal levels of proline in their blood.

Published Date: August 27, 2021
Published By: National Institutes of Health