Five patients aged 12 to 16 years old were admitted between 1987 and 1994 at the neurological unit because of uncontrolled epilepsy. They had had a normal development until the adolescence, when a history of poor school performance and memory difficulty started. It is emphasized the clinical sequence of dementia followed by tonic-clonic seizures and myoclonus, the positive family history and the difficult therapeutic management, in spite of multiple anticonvulsant combinations, including sodium valproate and clonazepam. The clinical and laboratory differential diagnosis were discussed to show that similar cases should be submitted to skin biopsy looking for Lafora bodies in apocrine and eccrine glands. However, the liver is considered as the most reliable site for the biopsy, which in our study showed positivity in four out of the five cases.