Heritability of cluster headache

We conducted a pedigree analysis in 222 patients with cluster headaches (CHs) in order to assess a familial predisposition to the disease. Heritability was determined by Falconer's index (from the incidence of CH among first degree relatives of probands compared with a control population), which varies between 0 and 1 (none or full genetic causation). A positive family history (I/II degree relatives) was found in 2.3% of our CH patients. Three generations were affected in one family and two generations in another two families. The calculated Falconer's heritability index was, however, only 0.26 ± 0.25 SD. Our study confirms a higher familial occurrence of CH, some families showing a pattern compatible with autosomal dominant inheritance with reduced penetrance. The low Falconer's index indicates, however, a large non-genetic causation in most cases of CH.