An epidemiological/genetic study of mental subnormality in Assiut Governorate, Egypt.

The aim of this investigation was to study the epidemiologic and genetic aspects of mental subnormality (MS) in Assiut Governorate, representing the Egyptian population. The sample comprised 3000 randomly selected subjects from three localities: one urban (Assiut City) and two adjacent rural villages. Age-matched controls were chosen for comparison. The Stanford-Binet test was administered to each individual. During history-taking special attention was paid to consanguinity and categorization on a genetic basis. The results revealed 116 cases with MS, showing an overall prevalence of 3.9%, which varied in the three locations: 3.4% in Assiut City, and 3.8% and 4.4% in the two rural locations. Clinico-genetic classification revealed the following: idiopathic MS 27.6%, MCA/MR syndromes 24.1%, primary CNS defect 12.9%, Martin-Bell syndrome 10.3%, inborn errors of metabolism 9.5%, tetratogenic and environmental causes 5.2%, MS and epilepsy 4.3%, chromosomal disorders 3.4% and MS associated with psychiatric disorder 2.6%. Parental consanguinity was found in 65% of the total sample, which emphasizes the role played by that factor in the etiology of mental subnormality in Egypt.