Inborn errors of metabolism form a large class of
genetic diseases involving
congenital disorders of
metabolism. The majority are due to defects of single
genes that code for
enzymes that facilitate conversion of various substances (
substrates) into others (
products). In most of the disorders, problems arise due to accumulation of substances which are toxic or interfere with normal function, or to the effects of reduced ability to synthesize essential compounds. Inborn errors of metabolism are now often referred to as
congenital metabolic diseases or
inherited metabolic diseases.