Mental retardation (MR) is classically deficits in adaptive behavior and manifest during the developmental period.
The causes of mental retardation were not understood in many cases. This study was undertaken to identify the etiologies of mentally retarded children enrolled in a special educational institution under the hypothesis that clarifying causes of MR
can
not only provide basic epidemiological data on MR in Korea, but also imply possibly preventable measures to avoid MR in some cases.
In this study, complete medical history was taken in addition to a thorough individual physical examination with collection of urine specimens for metabolic screening tests including ferric chloride, DNPH, nitrosonaphthol, nitroprusside, CTAB,
and
reducing substance tests in 259 mentally retarded children aged between 3 through 18 year old.
The cytogenetic, molecular genetic, and endocrine studies wire performed in 14 children with high clinical suspicion of chromosomal abnormalities and congenital hypothyroidism. Dysmorphism syndromes were delineated using computer software
software
program.
Definite or presumptive etiological diagnosis has been made in 122 (47%) mentally retarded children, Among three major identifiable causes, perinatal brain damage resulted from difficulties in labor, prematurity, kernicterus, and neonatal sepsis,
was
most commonly found in 57 children (22%), followed by chromosomal abnormalities including Down's syndrome and fragile-X syndrome in 35 children (13.5%), and dysmorphism syndrome in 10 children (3.9%) in order. Other identifiable causes for
mentally
retarded children were listed as autism (2.3%), endocrine & hereditary metabolic disease (1.9%), central nervous system malformations, neurophakomatoses (1.9%), and postnatal accidents, poisoning, infection (1.5%).
In conclusion, aforementioned data suggested that one fourth of MR can be avoided or treated by making efforts to improve peri, postnatal care and early detection. Routine urinary metabolic screening tests for inborn errors cannot be justified
though
CTAB test showed high specificity for the diagnosis of mucopolysaccharidosis. Some mentally retarded children's families need genetic counselling since Mendelian inherited disorders are culpable for causing MR in some children.
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