Unverricht-Lundborg disease: homozygosity for a new splicing mutation in the cystatin B gene.

Unverricht-Lundborg disease is the most common form of progressive myoclonic epilepsy (PME). It is due to cystatin B gene (CSTB) mutations. Several mutations in CSTB gene have been published, but few in homozygosity. We describe a patient with a new splicing alteration. Mutation Gln22Gln leads to abnormal splicing and partial inclusion of intronic sequence. This is one of the few cases of homozygosity for a non-classic mutation and adds to mutational heterogeneity of CSTB.