Frequency of the LRRK2 G2019S mutation in siblings with Parkinson's disease.

Background: Mutations in the LRRK2 gene, the most frequent of which is the G2019S mutation in exon 41, cause familial and sporadic Parkinson's disease (PD) with reduced penetrance.
Objectives: To assess the frequency of the LRRK2 G2019S mutation in families thought to have autosomal recessive PD (siblings but not their parents were affected) and to determine the clinical features of LRRK2 mutation carriers.
Methods: We sequenced both strands of exon 41 of the LRKK2 gene in 90 index cases from French and North African families in which PD might have been inherited as a recessive trait. Patients with mutations underwent detailed clinical evaluations.
Results: We found heterozygous G2019S mutations in 1 Algerian and 1 French family (overall relative frequency = 2.2%). Four LRRK2-positive patients had typical PD, but their Mini Mental State Examination (MMSE) scores were lower than those of patients without this mutation.
Conclusion: The LRRK2 G2019S mutation is as frequent in families with possible autosomal recessive PD (2.2%) as in the sporadic cases published elsewhere (1.9%). The clinical features in the LRRK2-positive patients were those of typical PD, except for lower MMSE scores.
(2007 S. Karger AG, Basel)