ABSTRACT
Hereditary metabolic disorders or inherited disorders of metabolism are mostly caused by gene mutations. There are hundreds of these disorders. In most Westernized countries, neonatal screening for these disorders is regularly performed. Disorders that affect metabolism of amino acids include maple syrup urine disease, hypermethioninemia, phenylketonuria, tyrosinemia, homocystinuria, argininemia, ornithinemia, and hyperinsulinism-hyperammonemia syndrome. Carbohydrate metabolism disorders include those affecting fructose metabolism (galactosemia and glycogen storage diseases). Fatty acid metabolism disorders result from an inability of the body to produce or utilize one enzyme that is required to oxidize fatty acids, the preferred energy source. Fatty acid oxidation disorders lead to the accumulation of fatty acids and decreased cell energy metabolism. Mitochondrial oxidation disorders are defined by a lack of cellular energy due to defective oxidative phosphorylation. Glycerol metabolism disorders involve elevated plasma and urine glycerol levels, plus neurometabolic manifestations, and can be life-threatening in children. Ketone metabolism disorders usually appear soon after birth or later in childhood and include ketonuria and metabolic acidosis. Purine metabolism disorders cause myalgias, cramping, immunodeficiency, lymphopenia, infections, spasticity, and kidney stones with hematuria. Purine salvage disorders progress to cause intellectual disability and spastic cerebral palsy. Lysosomal storage diseases may affect the skeletal muscles, brain, skin, heart, and central nervous system.
