Fumarase deficiency (fumaric aciduria) is a rare autosomal recessive metabolic disorder caused by deficient activity of fumarate hydratase (FH, fumarase), one of the constituent enzymes of the Krebs tricarboxylic acid cycle. Patients usually present early in infancy with a severe encephalopathy, including hypotonia, developmental retardation, and seizures. Many of them have died during the first several years of life.
