A group of genetic disorders that involve defects in certain enzymes, resulting in abnormal and damaging accumulations of substances called mucopolysaccharides in the tissues, medically classed as metabolic disorders or storage disorders. Each of the various MPS disorders has an MPS number and a name, the best-known being Hurler’s syndrome (MPS 1), Hunter’s syndrome (MPS II), and Morquio’s syndrome (MPS IV). Children affected with MPS generally have mental retardation, skeletal deformity (especially of the face), retarded growth often resulting in dwarfism, and a shortened life expectancy, often dying in childhood or adolescence, though some with a mild form of the disorder may live a relatively normal life. Other characteristics are specific to the individual types. There is as yet no specific treatment. The disorders can be detected before birth with prenatal testing, as through amniocentesis, or after birth through urinalysis and X- ray analysis of skeletal development. Parents with a family history of MPS may well want to seek genetic counseling before or early in pregnancy. Related storage disorders, each also with several variant forms, are mucolipidoses (ML), in which compounds called mucolipids accumulate, and lipid storage diseases (lipidoses).