Lafora disease is the most common teenage-onset progressive myoclonus epilepsy. There are two known recessive mutations in EPM2A or EPM2B genes, with possibly another mutation not yet identified.
It is a form of stimulus-sensitive myoclonic epilepsy. Onset is usually between 6 and 19 years of age, with peak at 15 years. Presenting feature most common is a single seizure in the second decade of life, followed by progressive myoclonus, myoclonic seizures, tonic-clonic seizures, focal occipital seizures, intellectual decline, and severe motor and coordination impairments. Most affected individuals do not live past the age of 25 (average survival is 6 years).
Lafora's bodies are concentric amyloid (mucopolysaccharide) bodies, and are present in the brain (in neurons), and also sometimes in the retina, heart, liver, muscle, bone, and skin.
Unverricht's disease is similar, but without Lafora's bodies on pathological study.