A group of genetic disorders that cause disruption of the chemical and physical processes by which food is broken down for use in the body. Dozens of such disorders are known, many of them extremely rare, but each of them caused by a defect in the production of a single enzyme or protein. Many of them are classed as storage disorders, because the deficiency leads to abnormal and damaging accumulation of certain compounds in the body tissues, often especially affecting the brain. Among the diseases regarded as metabolic disorders are phenylketonuria, galactosemia, various types of mucopolysaccharidoses (including Hurler’s syndrome, Hunter’s syndrome, and Morquio’s syndrome), mucolipidoses, lipid storage diseases (including Tay-Sachs disease and Gaucher’s disease), Lesch-Nyhan syndrome, and glycogen storage diseases. Diagnoses of such disorders are often made on the basis of the signs and symptoms linked with that particular disorder, often followed by liver function tests and kidney function tests. Some metabolic disorders can now be detected by using various kinds of genetic screening tests, such as amniocentesis or chorionic villus sampling. Sometimes treatment involves avoidance of particular types of foods or other things to which the body is sensitive; taking enzymes orally or by injection can, in some metabolic disorders, help make up the deficiency. Researchers have also shown some early, experimental success in gene therapy, transplanting healthy cells to replace deficient ones in some disorders, though therapy by manipulation of genes is still some distance in the future.
A collection of conditions characterized by disruptions in certain aspects of bodily chemistry. Certain metabolic disorders arise from a genetic malfunction or deficiency of an enzyme essential for a specific chemical process. Others stem from the inadequate or excessive production of a hormone that regulates metabolic functions, as seen in cases like diabetes mellitus and hypothyroidism.