PURPOSE OF REVIEW: Parkinson's disease is the second most common 
neurodegenerative disorder and affects 2% of the population over the age of 60 
years. Due to the increasing proportion of elderly individuals in developed 
countries, Parkinson's disease and related neurodegenerative disorders represent 
a growing burden on the health care system. In the majority of cases, the cause 
of the disease is still unknown, and its elucidation remains one of the major 
challenges of the neurosciences. Recent findings in rare genetic forms of 
Parkinson's disease have allowed the development of novel animal models, 
providing a basis for a better understanding of the molecular pathogenesis of 
the disease, setting the stage for the development of novel treatment 
strategies.
RECENT FINDINGS: Several novel genes for monogenic forms of Parkinson's disease, 
such as PINK-1 for an autosomal-recessive early-onset variant, and LRRK2 for a 
relatively common late-onset autosomal-dominant form have recently been 
discovered, and several novel animal models have been generated on the basis of 
genes that had been found earlier.
SUMMARY: The combination of genetic, pathologic and molecular findings provide 
increasing evidence that the pathways identified through the cloning of 
different disease genes are interacting on different levels and share several 
major pathogenic mechanisms.