Limits of clinical assessment in the accurate diagnosis of Machado-Joseph disease

I. Lopes-Cendes, I. Silveira, P. Maciel, C. Gaspar, J. Radvany, D. Chitayat, R. Babul, J. Stewart, M. Dolliver, Y. Robitaille, G. A. Rouleau and J. Sequeiros
Centre for Research in Neuroscience, Montreal General Hospital Research Institute, McGill University, Quebec.

BACKGROUND: Machado-Joseph disease (MJD) is a type of autosomal dominant spinocerebellar ataxia for which molecular diagnosis is available. We identified 4 families segregating the MJD mutation in which no unequivocal clinical diagnosis could be established prior to molecular testing. Ethnic background, clinical, and molecular characteristics of 19 individuals carrying the MJD mutation in these 4 families were compared with a group of 32 Portuguese families who were clinically diagnosed as having MJD and were found to carry the MJD mutation. RESULTS: Several factors seemed to have an impact in the accuracy of the clinical diagnosis, such as ethnic origin; the number of affected individuals available for examination in each family; the absence of patients showing specific clinical features, such as extrapyramidal signs; and the size of the expanded CAG repeat in the MJD gene. CONCLUSION: Since the recognition of MJD based solely on clinical grounds might sometimes be misleading, a search for the MJD mutation should be performed in patients with a clinical diagnosis of spinocerebellar degeneration.