Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. It most commonly follows an X-linked inheritance pattern, but is approximately equally prevalent in both males and females. This is because heterozygote females commonly manifest severe symptoms, an unusual situation in X-linked conditions. Due to the genes involved being essential to life, some of the genetic causes are extremely rare, in the order of 1 in millions. It affects a gene which codes for a critical enzyme complex, the Pyruvate dehydrogenase complex (PDC) which links the metabolic pathways of glycolysis and the citric acid cycle by transforming pyruvate into Acetyl CoA The pyruvate dehydrogenase complex facilitates oxidative decarboxylation, the chemical reaction between glycolysis and the citric acid cycle.