Available data are summarized concerning the presence of photoparoxysmal EEG response (PPR), associated or not with reflex myoclonus, appearing in rare genetic disorders or in a subset of epileptic syndromes mostly presenting in infancy or childhood and less often in young adulthood. In these disorders, PPR can be an early and primary finding or appear in association with other prominent signs of the disease. PPR rarely occur in acquired epilepsies, and usually associated with rather specific EEG and clinical pictures, thus suggesting the presence of a genetic trait. This trait is more often associated with benign epilepsies but also presents in severe disorders, indicating the need of a complex diagnostic workup.