A form of progressive myoclonic epilepsy
Diagnosis:
Clinical features plus EEG and pathology
Genetics:
EPM2A gene chr. 6q24, protein= laforin (a dual phosphatase),
EPM2B gene chr. 6q22.3 a.k.a. NHLRC1 gene, protein = malin (a E3 ubiquitin ligase)
Clinical features:
Age 10-18 y.o. epilepsy, segmental massive myoclonus, rapidly progressive mental deterioration (dementia), ataxia.
Findings on Investigations:
EEG:
- Fast spike-wave and poly-spike-wave complexes, photosensitivity, multifocal abnormalities.
- 50% have occipital spikes
Pathology:
Lafora bodies = intracellular periodic acid-Schiff-positive (PAS) inclusions (abnormal glucose polymer) in CNS (cortex & dentate nucleus), PNS, skin, liver or muscle.