Concordance of interstitial cystitis (IC) in identical twins: preliminary data

Abstract

If a disease is genetic, the closer the biologic relationship to an index case, the higher the prevalence of the disease. This is because monozygotic twins share all their genes; first-degree relatives (parents, siblings [including dizygotic twins], children) share half; second-degree relatives (aunts, uncles, nephews, nieces) share one fourth; and third-degree relatives (first cousins) share one eighth of their genes. Funded by the Fishbein Foundation, we collaborated with the Interstitial Cystitis Association (ICA) in performing a family survey of ICA members in the summer of 1999. Of the 2581 ICA respondents, 50 noted they were one of a pair of twins. We reproduced the methodology of Curhan et al. (J Urol 1999; 161:549) to define IC (see Table 1).