Inheritance of Photosensitivity

Abstract

To investigate the mode of inheritance of the photoparoxysmal response (PPR) and to obtain more information about the influence of photosensitivity on the seizure risk in siblings of patients with epilepsy. Examination of the records of families with one photosensitive parent (Group I, n = 54) and of families with a photosensitive proband, neither of whose parents was photosensitive (Group II, n = 72). At the age of maximum penetrance, between 5 and 15 years of age, 50% of the siblings in Group I were photosensitive, compared to only 15% in Group II. Siblings in Group I showed a higher seizure rate (19%) than siblings in Group II (4%, p < 0.005). The majority of photosensitive siblings had no seizures, but photosensitive siblings had a higher seizure risk than non-photosensitive siblings. The highest seizure risk was found in photosensitive siblings of Group I (33%) compared to 9% in non-photosensitive siblings (p < 0.05). Our findings show that a PPR in parents is a major determinant for the risk of a PPR in offspring. The results may indicate an autosomal-dominant transmission with age-dependent penetrance of the PPR. Photosensitivity is an important factor in the pathogenesis of seizure disorders in childhood.