Clinical diagnosis is still of the utmost importance and following our review of cases diagnosed using the strict criteria, 100% were homozygous for the expansion. However, now that there is a relatively simple direct genetic test, the diagnosis can be considered in more unusual cases. Genetic testing has been shown to be of value in establishing the correct diagnosis and in directing the appropriate screening tests, including cardiological assessment and blood sugar estimation. Perhaps the most interesting development following identification of the gene is the rapid progress in our understanding of the protein. If, as seems likely, it turns out to be a mitochondrial protein involved in iron transport, it gives cause for hope of effective treatment.