Down syndrome, increased risk of dementia and lipid disturbances.

Down syndrome (DS) is the most common chromosomal aberration and genetically determined cause of intellectual disability. DS patients often present with some congenital defects and chronic diseases, including early onset dementia, which affects 70% of DS patients over 55 years of age and has a clinical presentation similar to Alzheimer disease (AD). The symptoms of DS originate from excessive genetic material within the "critical region" of the 21st chromosome. The "critical region" encompasses genes potentially associated with increase risk of dementia, e.g. the APP gene (amyloid beta precursor protein) which leads to excessive amyloid beta production. Post-mortem studies of DS patients' brains revealed diffuse deposition of the insoluble form of amyloid beta (Aβ), which is a characteristic feature of AD. Moreover, those changes were commonly observed in subjects > 31 years old. The pathomechanisms of AD have not been fully elucidated and scientists are still searching for new risk factors that may contribute to the development of this common illness. Recent research proved that lipid disturbance, especially disorders in the metabolism of HDL (high density lipoprotein) may play a crucial role in this pathogenic process. There are many studies examining lipid and lipoprotein concentration in the DS population, but up to now there are insufficient studies comparing these parameters with memory impairment, which may be a useful model for better understanding of the dementia pathomechanism.