approximately 22%. The most common maternal AD were ulcerative colitis, rheumatoid arthritis, thyrotoxicosis, and multiple sclerosis, although power was limited to examine the risk for many of the individual AD.18 In two case-control family studies that analyzed the same Brazilian sample using different statistical approaches,19, 20 the rate of OCD and related disorders, including tic disorders, was significantly higher among first-degree relatives of individuals with rheumatic fever than among first-degree relatives of controls (14.7% vs 7.3%),19 and the risk of OCD and related disorders was increased by the presence of either rheumatic fever or Sydenham's chorea in another family member.20 Conversely, another family study21 found no significant differences in the rates of OCD in 72 mothers of children and adolescents with inflammatory bowel disease, compared to 44 mothers of children and adolescents with cystic fibrosis (a non-autoimmune genetic disease).
