Chromosomal Abnormalities.

Down syndrome (DS), caused by trisomy 21, is characterized clinically by somatic abnormalities, intellectual disabilities in children, and Alzheimer-type dementia in adults. The phenotype may vary, with minor brain anomalies such as hypoplasia of the superior temporal gyrus, brain stem, and cerebellum, decreased brain weight and rounded occipital poles [1]. Basal ganglia calcification is more frequently found in the region of the globus pallidus and putamen, and its incidence increases with age [2]. Dendrites gradually show abnormal arborization and decreased spines after 4 months of age [3,4]. Alzheimer-type dementia with neuritic plaques and neurofibrillary tangles develops in young adults. Senile plaques and cerebrovascular amyloidosis involve β-amyloid protein (Aβ). In Alzheimer-type dementia, Aβ42, which aggregates more rapidly than Aβ40, is a major component of diffuse (early) plaques, whereas Aβ43 demonstrates early axonal damage in diffuse plaques [5]. [ABSTRACT FROM AUTHOR]