Down Syndrome in Kuwait: Recurrent Familial Trisomy 21 in Siblings

Three young unrelated multiplex Kuwaiti families each confirmed to have 3 sibs with recurrent regular Trisomy 21 Down syndrome are reported. Chromosomal study of the parents showed normal karyotype for their mothers and two of their fathers (family II and III). These findings of multiplexes of regular Trisomy 21 patients resulted from the possibility of genetic predisposition for nondisjunction. Increased occurrence of Trisomy 21 in offspring of consanguineous marriages suggests that Trisomy 21 is etiologically heterogeneous and in a sub group of Trisomy 21 families nondisjunction may be genetically determined. In spite of extensive studies with regard to the origin of trisomy, the prime mechanism leading to recurrent Trisomy 21 or aneuploidy is not well understood. Genetic counselling of families with (maternal age <35 years), is a difficult task. Parental mosaicism, as well as "Genetic predisposition" should be considered in counselling families with sibships of regular trisomy-21.