Down syndrome is the most common of the chromosomal disorders. About 95% of affected persons have trisomy 21, so their chromosome count is 47. The parents of such children have a normal genetic make-up and are normal in all respects. Maternal age has a strong influence on the incidence of Down syndrome. It occurs in 1 in 1550 live births in women younger than 20 years, in contrast with 1 in 25 live births in women older than 45 years. Indeed, in 95% of cases the extra chromosome is of maternal origin. The reason for the increased susceptibility of the ovum to nondisjunction is not fully understood. No effect of paternal age has been found in those cases in which the extra chromosome is derived from the father. Down syndrome is a leading cause of severe mental retardation; approximately 80% of those afflicted have an IQ of 25 to 50. Ironically, these severely disadvantaged children may have a gentle, shy manner and may be more easily directed than their more fortunate normal siblings. Cardiac problems are responsible for a majority of the deaths in infancy and early childhood. Several other congenital malformations, including atresias of the esophagus and small bowel, also are common.
Down’s syndrome is not a death sentence even though there is no cure. Those diagnosed with the condition should seek medical attention early so that appropriate measures could be taken in helping them to achieve their full potential.