An epidemiological study of febrile seizures with special reference to family history and HLA linkage.

One hundred and forty four cases of febrile seizures, 95 simple (typical) and 49 complex (atypical); were studied and compared for clinical and epidemiological data and family history of febrile and afebrile seizures. Major results were: maximum age of onset below three years (75%) in both simple and complex groups, male preponderance, respiratory infection as the commonest etiology (69.4%) and maximum seizure onset within 24 hours of fever (73%). The familial prevalence of all seizures was 29.1%, 23.2% in the simple and 40.8% in the complex group (p < 0.01). The familial prevalence of febrile seizures was 20%; similar in both groups. The familial prevalence of afebrile seizures was 13.9%; 6.3% in simple and 28.6% in complex group (p < 0.01). The commonest relative was a sibling (13.2%). The prevalence in parents was 4%. Families with two additional members with history of seizures revealed complex seizure patterns in two-thirds of index cases. There was no correlation between family history of seizures and age at onset or sex. No clear inheritance pattern emerged and polygenic inheritance is likely. One third of eighteen families had siblings with identical segregation of parental HLA-A and B haplotypes. Five families showed the presence of HLA All. This small though adequate sample size did not reveal an HLA marker for febrile seizures.