PROGRESSIVE MYOCLONUS EPILEPSIES - CLINICAL AND GENETIC-ASPECTS

The progressive myoclonus epilepsies (PMEs) are a group of rare geneti c disorders previously shrouded in nosological confusion. Recent advan ces have clarified the features of these disorders and provided a rati onal approach to diagnosis. The major causes of PME are now known to b e Unverricht-Lundborg disease, myoclonus epilepsy ragged-red fiber (ME RRF) syndrome, Lafora disease, neuronal ceroid lipofuscinoses, and sia lidoses. Over the past 3 years, a series of molecular genetic findings have further refined the understanding of the PMEs. The specific muta tion responsible for many cases of MERRF has been identified, and the genes for Unverricht-Lundborg disease and for juvenile neuronal ceroid lipofuscinosis have been linked to chromosomes 21 and 16, respectivel y. Although the PMEs are among the rarest of the inherited epilepsies, because of molecular genetic discoveries they may soon be the best un derstood at the neurobiologic level.