Metabolic disorders in the aetiology of mental retardation

Abstract

In infancy and childhood the rapidly growing brain is particularly vulnerable to metabolic disorders. In this chapter only inborn (hereditary) errors of metabolism will be discussed. Many different metabolic pathways may be involved such as those of the amino acids, carbohydrates and lipids, plasma proteins, mucopolysaccharides, vitamins, pterins, hormones, electrolytes, trace elements, bilirubin, etc. (Table 1). In a catalogue of 170 inborn metabolic errors (McKusick, 1978), in which altered activity of a specific enzyme has been demonstrated, 70 were associated with more or less severe brain damage. Of 89 well defined disorders with oligophrenia (Eggers and Bickel, 1974), 41 were due to various inborn errors of metabolism, 48 to other causes such as chromosomopathies (12), inherited syndromes affecting the brain, eyes, ears and skin (12), heredodegenerative disorders (11), embryofetopathies (4), multiple malformations (7) and psychotic disturbances with dementia (2). Table 2 lists 50 metabolic disorders, with 70 subtypes, which are usually associated with brain damage. In some instances the number of cases recorded so far is too small for a definite statement that oligophrenia and heredity are essential features of the condition.KeywordsMental RetardationInborn ErrorBrain DamageMaple Syrup Urine DiseasePhenylalanine HydroxylaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.