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Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene represent the most common known genetic cause of inherited and idiopathic Parkinson's disease (PD) in different populations. The predicted multifunctionality of LRRK2 product and the pleomorphic pathology associated with LRRK2 mutations place this gene as a potential candidate for other neurodegenerative disorders, mainly Alzheimer's disease (AD). We report a Brazilian male expressing both late-onset AD and slowly progressive parkinsonism signs, and who presented the most frequent LRRK2 mutation (p.G2019S). Although the co-occurrence of PD and AD would be expected occasionally, the shared mechanisms between the two complex disorders are still unclear and are discussed herein. In light of recent findings about the wide role of LRRK2 under normal and pathological conditions, it is tempting to speculate that LRRK2 mutations might play an upstream influence on the etiology of not just PD but also several alpha-synuclein and tau pathologies, including AD.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene have emerged as a potential common cause for both sporadic and familial Parkinson’s Disease (PD) in different populations. The pleomorphic features exhibited by LRRK2 mutation carriers and the central role of Lrrk2 protein in the proper functioning of central nervous system suggest that mutations in this protein might be involved in multiple cellular processes leading to other neurodegenerative disorders than PD. The location of LRRK2 gene on chromosome 12, close to a linkage peak for familial late-onset Alzheimer’s Disease (AD), highlights that LRRK2 mutations might be involved in AD pathogenesis. We screened the most common LRRK2 mutation (p.G2019S) in a series of 180 consecutive patients clinically diagnosed with Alzheimer Disease (AD). We identified the p.G2019S in one AD patient with no PD signs, indicating that this mutation is not a common etiological factor for AD in our population (0.5%), corroborating recent data found in Norwegian, North American, Chinese and Italian populations. Nevertheless, these observations together with new information about the Lrrk2 critical multifunctionality do not rule out the possible influence of other variants within LRRK2 in AD, so that other screenings focusing in the whole extension of the LRRK2 using larger sized confirmed AD sample are urgently needed.

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