What Your Test Results Mean:

Carriers typically show no symptoms of 3-phosphoglycerate dehydrogenase deficiency; however, carriers are at an increased risk of having a child with 3-phosphoglycerate dehydrogenase deficiency. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor for more detailed risk assessment.

Disease Explained:

3-phosphoglycerate dehydrogenase deficiency is an inherited condition that prevents the body from synthesizing the amino acid serine. Serine is very important in the brain in the formation of neurotransmitters, neuron cell membranes, and myelin sheath to protect the neurons. The lack of serine causes serious neurological symptoms. Individuals with the more severe infantile onset form may have small head size identifiable by ultrasound during pregnancy. They also typically have recurrent seizures and psychomotor delays within the first year of life. In juvenile onset 3-phosphoglycerate dehydrogenase deficiency, mild developmental delay and seizures are common. Administration of serine during pregnancy has been used to manage the infantile onset form and oral serine has proven to prevent seizures in the juvenile onset form.

How the Genetics Works:

3-phosphoglycerate dehydrogenase deficiency is an autosomal recessive disorder caused by pathogenic variants in the PHGDH gene. In general, individuals have two copies of the PHGDH gene. Carriers of 3-phosphoglycerate dehydrogenase deficiency have a single variant in one copy of the PHGDH gene while individuals with 3-phosphoglycerate dehydrogenase deficiency have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.