Chapter 1 - Down syndrome: history and overview

Abstract

John Haydon Langdon Down was the first to characterize Down syndrome (DS) with facial features reminiscent to Blumenbach's Mongolian race. Hence, the syndrome was known much as “mongoloid” or "Down's syndrome." However, neither descrtibing the features of a genetic disorder based on some features of a race was justified nor the use of eponym such as Down's syndrome was approved. Down syndrome as the ideal name was demonstrated by the National Institute of Health, the United States. Males with DS are more affected than the females. The disease occurs in all populations at all geographical territories, though Hispanics are at a higher risk compared to other population. The syndrome is caused by trisomy 21 or presence of three copies of the chromosome 21, which is highly influenced by the maternal age and caused by nondisjunction or mis-segregation of chromosomes, most likely during meiosis or gametogenesis. As such, the risk of recurrence is negligible; however, if parental Robertsonian translocation or balanced translocation contributes to the trisomy 21, there would be a hereditary factor to increase the risk of recurrence. More so, if one of the parents carries a Robertsonian translocation involving both 21s, their 100% pregnancies will have trisomy 21 or DS. Therefore, genetic characterization or karyotyping of the affected child and both parents is essential before planning of future pregnancy.