UNVERRICHT-LUNDBORG DISEASE - ABSENCE OF NONALLELIC GENETIC-HETEROGENEITY

Unverricht-Lundborg disease is a clinically recognizable form of progr essive myoclonus epilepsy. Recently, in several families of both Finni sh and Mediterranean extraction segregating Unverricht-Lundborg diseas e, the gene for this disease was linked to the same region of the long arm of chromosome 21. We performed linkage analysis in eight families , including four of neither Baltic nor Mediterranean origin, using a p olymorphic (CA)n repeat marker for the human liver-type 6 phosphofruct okinase (PFKL) gene, previously mapped to 21q22.3. No recombinations w ere observed between the disease phenotype and the PFKL marker and a m aximum lod score of 5.63 was obtained. These findings confirm tight li nkage between PFKL and the gene for Unverricht-Lundborg disease and st rongly suggest a lack of nonallelic genetic heterogeneity of the disea se.