All of the following may occur in Down's syndrome except :

Answer is B (Undescended testis): Health concerns observed in people with Down syndrome : Sixty to 80 per cent of children with Down syndrome have hearing deficits. Foy to 45 per cent of children with Down syndrome have congenital hea disease. ASD and VSD are the most common forms of congenital hea diseases seen. Intestinal abnormalities also occur at a higher frequency in children with Down syndrome. Esophageal atresia, duodenal atresia and anal abnormalities are not uncommon in infants with Down syndrome. Children with Down syndrome often have more eye problems than other children who do not have this chromosome disorder. Eye problems such as strabismus, refractive errors and other eye conditions are frequently observed in children with Down syndrome. Brushfield's spots are whitish speckling on iris seen in light skinned people. Thyroid dysfunctions are more common in children with Down syndrome than in normal children. Between 15 and 20 per cent of children with Down syndrome have hypothyroidism. It is impoant to identify individuals with Down syndrome who have thyroid disorders since hypothyroidism may compromise normal central nervous system functioning. Skeletal problems have also been noted at a higher frequency in children with Down syndrome, including : patellar subluxation (incomplete or paial dislocation), hip dislocation, and atlantoaxial instability. Approximately 15 per cent of people with Down syndrome have atlantoaxial instability. Other impoant medical aspects in Down syndrome, including immunologic concerns, leukemia, Alzheimer disease, seizure disorders, sleep apnea and skin disorders. Undescended testis has not been described as an association with Down's syndrome.