Genetic findings have changed our views on Parkinson's disease (PD) and 
parkinsonism, which will be collectively referred to as Parkinsonian Syndrome 
(PS) in the present manuscript. Mutations in several genes are found to cause 
monogenic forms of the disorder. Point mutations, duplications and triplications 
in the alpha-synuclein gene cause a rare dominant form of PS in families. 
Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene have been identified 
as a much more common cause for dominant PS, especially in certain ethnic 
groups, while mutations in the parkin gene, in DJ-1, PINK1 and ATP13A2 cause 
autosomal recessive parkinsonism of early onset. The monogenic variants are 
important tools in identifying cellular pathways that also shed light on the 
molecular pathogenesis of sporadic PS and some of these genes may play a role in 
the etiology of the common sporadic form of PS. Here we add recent findings to a 
greatly challenging puzzle.