PME is characterized by myoclonus, tonic-clonic seizures and progressive neurologic dysfunction, particularly ataxia and dementia.  Myoclonus in PME is typically fairly severe and often precipitated by posture, action and sensory stimulation in a wide range of modalities. 

The symptoms and signs in patients with primary generalized epilepsy, particularly juvenile myoclonic epilepsy, may mimic those of the PME phenotype.  This is particularly true if toxicity arises from anticonvulsants, since the latter may cause ataxia, uncontrolled seizures and cognitive impairment.

PME also needs to be distinguished from other secondary generalized epileptic encephalopathies, such as the Lennox-Gastaut syndrome.  The epileptic encephalopathies are characterized by various forms of generalized seizures, including myoclonic seizures, but frequently have a fixed neurological deficit, although the illness may progress in some cases.  PME can usually be distinguished from secondary generalized epileptic encephalopathies by a history of normal development followed by a relatively rapid progression of symptoms after the illness starts. 

  1. Unverricht-Lundborg Disease    
  2. Lafora Body Disease
  3. Neuronal Ceroid Lipofuscinoses               
  4. Gm2 Gangliosidoses      
  5. Sialidosis             
  6. Mitochondrial Disease  
  7. Neuroserpin Mutations
  8. Hallervorden-Spatz Syndrome
  9. Juvenile Neuroaxonal Dystrophy             
  10. Coeliac Disease
  11. Biotin Deficiency             
  12. Gaucher Disease
  13. Angelman Syndrome    
  14. Rett Syndrome