Another cause of vaccine encephalopathy: a case of Angelman syndrome.

Dravet syndrome has been found recently as an important underlying condition in cases of alleged vaccine encephalopathy after pertussis vaccination, where vaccination seemed to have precipitated the occurrence of the disease without modifying the long-term course. We report on a patient diagnosed with Angelman syndrome in her fifth decade, in whom the intellectual disability and epilepsy had been assumed to be caused by a vaccine encephalopathy following smallpox vaccination. Clinical features of Angelman syndrome had faded away. The history of the present patient suggests that genetic conditions other than Dravet syndrome can be associated with an alleged vaccine encephalopathy. A history of vaccine encephalopathy is rare among patients with learning disability and refractory epilepsy (1.4% in our cohort), but it should lead to consideration of a comprehensive genetic work-up if Dravet syndrome is excluded. The early history of the patient, when available, should guide the investigations. Medico-legal aspects are also discussed.