Segregation analysis of juvenile myoclonic epilepsy

We examined the inheritance of juvenile myoclonic epilepsy (JME). We looked at both the trait of "epilepsy" and the trait of "epilepsy-plus-EEG abnormalities," since EEG abnormalities are frequently found in the clinically unaffected sibs of JME patients. We tested several modes of inheritance including the fully penetrant recessive and several two-locus models. We could reject all models tested (fully penetrant single-locus and two-locus models) when abnormal EEGs were classified as "unaffected." We could also reject the fully penetrant single locus models when family members with abnormal EEGs were considered "affected." We also rejected the two-locus model where the inheritance at both loci was dominant. The two-locus model where both loci showed recessive inheritance could not be rejected, nor could the model where one locus was dominant and the other recessive. Our results suggest that the underlying predisposition for JME is genetically determined and is partially reflected in the abnormal EEGs found in clinically unaffected family members.