The cystatin B-deficient (Cstb−/−) mouse, generated by targeted disruption of the Cstb gene resulting in complete loss of CSTB protein, was described more than 25 years ago as a model for progressive myoclonus epilepsy type 1 (EPM1, Unverricht-Lundborg disease, OMIM #254800; Pennacchio et al., 1998). This evidence concerns the gene CSTB and Unverricht-Lundborg disease.