Genetic factors in febrile convulsions. An investigation of 64 same-sexed twin pairs.

Abstract

The importance of genetic factors in the aetiology of febrile convulsions (FC) has been evaluated from a study of 64 same-sexed twin pairs and their siblings. The twin pairs were selected from a twin population of 1631 normal same-sexed twin pairs. Eight of the 26 monozygotic (MZ) pairs were concordant with respect to FC, while the non-proband of one further MZ pair suffered from petit mal epilepsy. Five of the 37 dizygotic (DZ) pairs were concordant with respect to FC. The pairwise concordance rates for the MZ and DZ series were 0.28 and 0.11 respectively (chi2= 1.82, 0.10 < p < 0.20), while the MZ and DZ proband concordance rates were 0.46 and 0.20 respectively. The MZ pairwise concordance rate of 0.57 was significantly higher than the DZ concordance rate of 0.09 in the 30 female pairs (chi2= 5.77, 0.01 < p < 0.02). The incidence of FC in sibs of the propositi was 14%. The combination of a high risk of FC in the sibs of the propositi and the non-significant difference between the concordance rates in MZ and DZ pairs indicates that FC are caused by factors shared by sibs, but that these factors are to a great extent of a non-genetic nature. However, the separate analysis of the female pairs demonstrates the existence of genetic aetiological factors.