A rare group of disorders characterized by the development of myoclonic and tonic-clonic epileptic seizures associated with progressive degeneration of the nervous system. The disease is progressive myoclonus epilepsy (MONDO_0020074, a Monarch Disease Ontology term). Also known as: PME, epilepsy, progressive myoclonic, progressive myoclonic epilepsy, progressive myoclonic epilepsy (disorder) [ambiguous].