Clinical and genetic study of essential tremor in the Italian population

Essential tremor (ET) is one of the most common movement disorders. The pat hogenesis is as yet unknown, although a genetic cause has long been recogni sed. Clinical and molecular evidence suggested that the ET gene contains a CAG expanded region. We examined a cohort of 240 Italian ET patients, class ified as familial (193 cases) and sporadic (47 cases). The clinical manifes tations of ET patients confirmed that the disorder is characterised by a la rge phenotypic variability. Repeat expansion detection (RED) approach did n ot demonstrate large CAG expansions. Six families were genotyped with 12 mi crosatellites markers of 2p and 3q regions and analysed according to parame trical methods. Lod scores values obtained in these families excluded the a ssociation of ET with 2p and 3q loci. Our findings confirm the presence of genetic heterogeneity and suggest that at least a third locus is involved i n the pathogenesis of familial essential tremor.