LRRK2 and Parkinson disease: First characterized in genetic studies of affected families in England and in the Basque region in northern Spain [1], [2], mutations in leucine-rich repeat kinase 2 (LRRK2) have been identified as the underlying cause of up to 10% of familial PD cases and 2–3% of sporadic cases, with varying numbers and allele distribution depending upon the populations studied [3], [4].