Prevalence of interstitial cystitis in first-degree relatives of patients with interstitial cystitis

To compare, in a pilot study, the prevalence of interstitial cystitis (IC) among first-degree relatives of patients with IC with the prevalence of IC in the general population. Often the first evidence that a disease may have a genetic susceptibility is the demonstration of family aggregation of the disease.

Members of the Interstitial Cystitis Association (ICA) were mailed a survey inquiring about the prevalence of the disease or consistent symptoms in first-degree family members (parents, siblings, and/or children). The same survey instrument was used in telephone interviews of a randomly selected sample of nonrespondents to determine the degree of responder bias.

Of 2581 respondents to the mail-in survey, 101 (3.9%) reported 107 first-degree relatives with IC. The subsequent telephone interviews with 346 randomly selected nonrespondents revealed little selection bias in the mail-in survey. These measurements, plus data-based assumptions of proportions of those self-reporting IC who actually met the hydrodistension requirements for the diagnosis of IC, suggest that women, 31 to 73 years old who were first-degree relatives of patients with IC, themselves had a prevalence of IC of 995/100,000. A comparison of this with the number approximating the prevalence in the general population of American women of this age (60/100,000) indicates a risk ratio for IC in adult female first-degree relatives of 17.

Adult female first-degree relatives of patients with IC may have a prevalence of IC 17 times that found in the general population. This, together with previously reported evidence showing a greater concordance of IC among monozygotic than dizygotic twins, suggests, but does not prove, a genetic susceptibility to IC.