Familial occurrence of dementia and parkinsonism: a systematic review.

Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are common clinical dementias characterized neuropathologically by the presence of cortical Lewy body pathology and with distinct clinical and neurobiological similarities. Importantly, genetic factors seem to play a key role in the pathogenesis of Parkinson's disease. In the current article, we examine the evidence for a genetic component to DLB and PDD by reviewing studies of familial PDD and DLB as well as familial coincidental PDD and DLB, and report the genes involved. There is a convincing genetic overlap between both syndromes, suggesting that they share a common etiological factor.