Pyruvate dehydrogenase E1-beta deficiency

Pyruvate dehydrogenase E1-beta deficiency is an extremely rare inborn error of energy metabolism caused by pathogenic variants in the PDHB gene, which encodes the E1-beta subunit of the pyruvate dehydrogenase complex (PDC). The pyruvate dehydrogenase complex is a critical mitochondrial enzyme that converts pyruvate to acetyl-CoA, linking glycolysis to the citric acid cycle. When this enzyme is deficient, the body cannot efficiently generate energy through aerobic metabolism, leading to accumulation of pyruvate and lactic acid. This primarily affects tissues with high energy demands, particularly the brain and nervous system. Clinical features of pyruvate dehydrogenase E1-beta deficiency typically present in infancy or early childhood and include lactic acidosis, developmental delay, intellectual disability, hypotonia, seizures, and progressive neurological deterioration. Structural brain abnormalities may be observed, including cerebral atrophy and abnormalities of the corpus callosum or basal ganglia. The severity of the condition can vary, ranging from severe neonatal lactic acidosis to milder forms with later-onset neurological symptoms. There is no cure for this condition. Management is primarily supportive and may include a ketogenic diet, which provides an alternative energy source (ketone bodies) that bypasses the need for the pyruvate dehydrogenase complex. Thiamine (vitamin B1) supplementation may be tried, as thiamine pyrophosphate is a cofactor for the PDC, though responsiveness varies. Dichloroacetate has been used in some cases to help reduce lactic acid levels. Avoidance of high carbohydrate intake is generally recommended to minimize pyruvate and lactate production. Prognosis depends on the severity of the enzymatic deficiency and the degree of neurological involvement.

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