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What is hyperprolinemia type II?
Hyperprolinemia type II is a rare metabolic disorder characterised by abnormally high levels of an amino acid called proline in the blood. The proline level is observed to be 10 to 15 times higher than normal and results from the deficiency of a breakdown enzyme known as delta-pyrroline-5-carboxylate dehydrogenase.
What are its main signs and symptoms?
Signs and symptoms may vary in severity, and commonly include:
- Proline levels in the blood are 10 to 15 times higher than normal
- Excessive amount of a compound called pyrroline-5-carboxylate in the body
- Mild mental retardation
- Intellectual disability
- Seizures
- Nephropathy
A less commonly occurring symptom is schizophrenia.
Conditions associated with hyperprolinemia include:
- Liver disease
- Malnutrition
- Lactic acidosis
What are its main causes?
Hyperprolinemia type II is the result of a mutation in the gene that gives instructions for the production of an enzyme called pyrroline-5-carboxylate dehydrogenase.
It is an autosomal recessive disorder wherein both parents of the affected individual will have a copy of the mutated gene, but do not show any signs and symptoms.
Hyperprolinemia is a disorder occurring at birth and affects both males and females equally.
How is it diagnosed and treated?
Rare diseases are often a challenge to diagnose and require a thorough medical history, careful physical examination and lab investigations.
Diagnosis of hyperprolinemia type II is based on the history, symptoms, elevated blood proline levels and elevated pyrroline-5-carboxylate levels in the urine.
Blood proline levels in hyperprolinemia type II may be elevated to 1900-2000 units (normal blood proline levels are about 450 units).
Hyperprolinemia type II should be differentiated from hyperprolinemia type I where there is a deficiency of an enzyme called proline oxidase. The blood proline levels in type I is 3 to 10 times higher than normal as compared to 10 to 15 times in type II.
Tests for determining the cause of hyperprolinemia include:
- New-born screening test
- Genetic testing
Genetic testing identifies abnormalities in chromosomes, genes or proteins.
Several methods can be used for genetic testing, such as:
- Molecular genetic tests
- Chromosomal genetic tests
- Biochemical genetic tests
There is no specific treatment for hyperprolinemia.
Restricting proline in the diet results in only a modest reduction in symptoms or may not even make a difference.
Symptoms of convulsions present during childhood resolve on their own, and the adult life appears to be symptom-free.
