Characterization of PLA2G6 as a locus for dystonia-parkinsonism
Although many recessive loci causing parkinsonism dystonia have been identified, these do not explain all cases of the disorder. We used homozygosity mapping and mutational analysis in three individuals from two unrelated families who presented with adult-onset levodopa-responsive dystonia-parkinsonism, pyramidal signs and cognitive/psychiatric features, and cerebral and cerebellar atrophy on magnetic resonance imaging but absent iron in the basal ganglia. We identified areas of homozygosity on chromosome 22 and, subsequently, PLA2G6 mutations. PLA2G6 mutations are associated with infantile neuroaxonal dystrophy and have been reported previously to cause early cerebellar signs, and the syndrome was classified as neurodegeneration with brain iron accumulation (type 2). Our cases have neither of these previously pathognomic features. Thus, mutations in PLA2G6 should additionally be considered in patients with adult-onset dystonia-parkinsonism even with absent iron on brain imaging.