Stefin B (cystatin B) is an intracellular inhibitor of cysteine cathepsins and mutations in the stefin B gene, resulting in the development of Unverricht-Lundborg disease, which is a form of myoclonic epilepsy.
CSTB-deficient mice, produced by targeted disruption of the mouse Cstb gene, display a phenotype similar to the human disease, with progressive ataxia and myoclonic seizures.
DNA deamination enables direct PCR amplification of the cystatin B (CSTB) gene-associated dodecamer repeat expansion in myoclonus epilepsy type Unverricht-Lundborg.
CSTB homozygous knockout mice show some parallels to the phenotype of human EPM1 including myoclonic seizures, development of ataxia and neuropathological changes associated with cell loss via apoptosis.
The still-unknown relationship between the pathologic level of ASA activity and myoclonic epilepsies suggests introduction of ASA assays in patients with PME.