jueves, 5 de junio de 2014

Phosphoglycerate dehydrogenase deficiency - Genetics Home Reference

Phosphoglycerate dehydrogenase deficiency - Genetics Home Reference

Genetics Home Reference: your guide to understanding genetic conditions

Phosphoglycerate dehydrogenase deficiency

Reviewed May 2014

What is phosphoglycerate dehydrogenase deficiency?

Phosphoglycerate dehydrogenase deficiency is a condition characterized by an unusually small head size (microcephaly); impaired development of physical reactions, movements, and speech (psychomotor retardation); and recurrent seizures (epilepsy). Different types of phosphoglycerate dehydrogenase deficiency have been described; they are distinguished by their severity and the age at which symptoms first begin. Most affected individuals have the infantile form, which is the most severe form, and are affected from infancy. Symptoms of the juvenile and adult types appear later in life; these types are very rare.
In phosphoglycerate dehydrogenase deficiency there is a progressive loss of brain cells leading to a loss of brain tissue (brain atrophy), specifically affecting the fatty tissue known as myelin that surrounds nerve cells (hypomyelination). Frequently, the tissue that connects the two halves of the brain (corpus callosum) is small and thin, and the fluid-filled cavities (ventricles) near the center of the brain are enlarged. Because development of the brain is disrupted, the head does not grow at the same rate as the body, so it appears that the head is getting smaller as the body grows (progressive microcephaly). Poor brain growth leads to an inability to achieve many developmental milestones such as sitting unsupported and speaking. Many affected infants also have difficulty feeding.
The seizures in phosphoglycerate dehydrogenase deficiency can vary in type. Recurrent muscle contractions called infantile spasms are typical early in the disorder. Without early treatment, seizures may progress to tonic-clonic seizures, which involve a loss of consciousness, muscle rigidity, and convulsions; myoclonic seizures, which involve rapid, uncontrolled muscle jerks; or drop attacks, which are sudden episodes of weak muscle tone.
Individuals with the infantile form of phosphoglycerate dehydrogenase deficiency develop many of the features described above. Individuals with the juvenile form typically have epilepsy as well as mild developmental delay and intellectual disability. Only one case of the adult form has been reported; signs and symptoms began in mid-adulthood and included mild intellectual disability; difficulty coordinating movements (ataxia); and numbness, tingling, and pain in the arms and legs (sensory neuropathy).

How common is phosphoglycerate dehydrogenase deficiency?

This condition is likely a rare disorder, but its prevalence is unknown. At least 15 cases have been described in the scientific literature.

What genes are related to phosphoglycerate dehydrogenase deficiency?

Mutations in the PHGDH gene cause phosphoglycerate dehydrogenase deficiency. The PHGDH gene provides instructions for making the parts (subunits) that make up the phosphoglycerate dehydrogenase enzyme. Four PHGDH subunits combine to form the enzyme. This enzyme is involved in the production of the protein building block (amino acid) serine. Specifically, the enzyme converts a substance called 3-phosphoglycerate to 3-phosphohydroxypyruvate in the first step in serine production. Serine is necessary for the development and function of the brain and spinal cord (central nervous system). Serine is a part of chemical messengers called neurotransmitters that transmit signals in the nervous system. Proteins that form cell membranes and myelin also contain serine. Serine can be obtained from the diet, but brain cells must produce their own serine because dietary serine cannot cross the protective barrier that allows only certain substances to pass between blood vessels and the brain (the blood-brain barrier).
PHGDH gene mutations result in the production of an enzyme with decreased function. As a result, less 3-phosphoglycerate is converted into 3-phosphohydroxypyruvate than normal and serine production is stalled at the first step. The lack of serine likely prevents the production of proteins and neurotransmitters in the brain and impairs the formation of normal cells and myelin. These disruptions in normal brain development lead to the signs and symptoms of phosphoglycerate dehydrogenase deficiency.
Read more about the PHGDH gene.

How do people inherit phosphoglycerate dehydrogenase deficiency?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about diagnosis or management of phosphoglycerate dehydrogenase deficiency?

These resources address the diagnosis or management of phosphoglycerate dehydrogenase deficiency and may include treatment providers.
You might also find information on the diagnosis or management of phosphoglycerate dehydrogenase deficiency in Educational resources and Patient support.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.

Where can I find additional information about phosphoglycerate dehydrogenase deficiency?

You may find the following resources about phosphoglycerate dehydrogenase deficiency helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for phosphoglycerate dehydrogenase deficiency?

  • 3-PGDH deficiency
  • PHGDH deficiency
  • 3-phosphoglycerate dehydrogenase deficiency
For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about phosphoglycerate dehydrogenase deficiency?

Where can I find general information about genetic conditions?

What glossary definitions help with understanding phosphoglycerate dehydrogenase deficiency?

References (7 links)

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.

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