SBMA, SCA1 and DM are all neuromuscular disorders which have very different presentation with varying degrees of severity but with a common feature of muscular weakness. In addition they all show anticipation correlating with the length of an unstable trinucleotide repeat. It is possible that trinucleotide repeat expansions will underlie other hereditary neuromuscular disorders, for example spinocerebellar ataxia type 2 (mapped to 12q and with similar symptoms to SCA1 including anticipation) is a prime candidate (30). The biochemical effects of these expansions have not yet been elucidated and therefore effective therapeutic interventions cannot currently be designed for affected individuals. However, the relative ease of diagnosis and the availability of accurate prenatal testing have already had a significant impact on the patient groups.