NeurometPlus

Incidence

Autosomal recessive. Rare condition, often asymptomatic.

Clinical Characteristics

Two types of hyperprolinemia are recognized by physicians and clinical researchers. Each represents an inherited inborn error of metabolism involving the amino acid, proline. Proline is abundant in nature and readily found in a variety of foods. Hyperprolinemia Type I (HP-I) is characterized by abnormally high levels of proline in the blood. The high level of blood proline is the result of a deficiency of the enzyme proline oxidase, which is essential to the normal breakdown (metabolism) of proline. There are often no clinical manifestations of HP-1. In the affected infant reported by Oyanagi et al. (1987), who also had a chromosomal abnormality, proline oxidase activity of liver tissue obtained by biopsy was about 9% of that of controls. Restriction of dietary proline resulted in a prompt fall of plasma proline levels with satisfactory growth, but no improvement in mental development. The patient had the facial appearance characteristic of hyperprolinemia and suffered from convulsions beginning at age 10 months. The aminoaciduria includes hydroxyproline and glycine as well as proline, presumably because these 3 amino acids share a renal tubular active transport mechanism which is overloaded by the high level of proline in the glomerular filtrate. In hyperprolinemia type I, the defect involves the enzyme proline oxidase (Efron, 1965). Mental retardation is not a feature.

Precipitants

None

Provocation Tests

None

Diagnostic Procedures

Aminoacids in plasma and urine quatitative. Proline oxidase activity of liver tissue obtained by biopsy may confirm Dx.