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Most inherited disorders (also called inborn errors) of metabolism are caused by mutations in genes that code for enzymes; enzyme deficiency or inactivity leads to accumulation of substrate precursors or metabolites or to deficiencies of the enzyme's products. Hundreds of disorders exist, and most are extremely rare; they are typically grouped by the affected substrate (eg, carbohydrates, amino acids, fatty acids).
Most states routinely test all neonates for specific inherited disorders of metabolism and other conditions (see Approach to the Care of Normal Infants and Children: Screening), including phenylketonuria, tyrosinemia, biotinidase deficiency, homocystinuria, maple syrup urine disease, and galactosemia. Some states also include testing for disorders of fatty acid oxidation and other organic acidemias.
Metabolic defects that primarily cause disease in adults (eg, gout, porphyria), are organ-specific (eg, Wilson's disease, congenital adrenal hypoplasia), or are common (eg, cystic fibrosis, hemochromatosis) are discussed elsewhere in The Manual. Inherited disorders of lipoprotein metabolism are listed in see Table 3: Lipid Disorders: Genetic (Primary) Dyslipidemias .
Last full review/revision November 2005
Content last modified November 2005
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