Aetiological evaluation of mental retardation in Brazilian patients

Abstract

INTRODUCTION: Mental retardation is present in approximately 2-3 % of the population. Clinical geneticists are frequently asked to evaluate children with development delay or mental retardation. Identifying the cause of the mental retardation will benefit individuals and families, answering questions about management, prognosis, recurrence risks and prevention.
MATERIAL AND METHODS: A genetic diagnostic survey in a population of 260 mentally retarded institutionalized patients in the South of Brazil is presented.
RESULTS: The patients had a male:female ratio of 1.3:1 and their ages varied from 1 month to 47 years with a mean of 5 years and one month. Using personal and family data,  careful clinical examination and laboratory investigation, the authors established a definitive diagnosis in 171 patients (65.76%). A constitutional disorder was present in 147 patients (56.53%).
CONCLUSION: Down syndrome patients represented 32.30% and 3,84% had other chromosomal anomalies, including microdeletion syndromes. In 32 patients (12.30%) a mendelian inheritance disorder was diagnosed. In eleven patients (4.23%) a MCA/MR syndrome was recorded. Ten patients (3.84%) presented a CNS malformation. An acquired condition was observed in 26 patients (10%), representing 7.69 % of CNS dysfunction, 2.3% of pre- or postnatal infection and 0.4% of postnatally acquired conditions other than infections. In the remaining 87 patients (34.46%) a conclusive diagnosis was not possible.