Aggregation of autoimmunity in extended families of people with autoimmune Addison disease

Background Autoimmunity accounts for 90% of cases of primary adrenal insufficiency (Addison disease (AD)). Affected people present a significant co-occurrence of autoimmune conditions; hence, clustering of autoimmunity is also predicted among their relatives. Aims To evaluate the burden of autoimmunity in families of people with AD. Methods A total of 116 individuals with AD was surveyed regarding the occurrence of 23 autoimmune diseases among their relatives. Results A total of 74.1% of persons with AD reported at least one relative with an autoimmune disorder - 257 cases were diagnosed in 221 relatives. Hashimoto thyroiditis was found in 100 individuals, followed by Graves disease and vitiligo, in 25 and 24 relatives respectively. Type 1 diabetes was diagnosed in 23 relatives, psoriasis in 15, rheumatoid arthritis in 12, pernicious anaemia in 11, multiple sclerosis in 8, and premature menopause in 8 women. AD was found in seven relatives, alopecia in six and celiac disease in five. Other conditions were rare. Significant correlation was noticed between the number of autoimmune conditions in AD proband and the number of affected relatives (P = 0.031). A total of 66.4% of people with AD had a first-degree relative suffering from autoimmunity. Autoimmune conditions were more frequent among females: sisters (P < 0.001), mothers (P = 0.002) and grandmothers (P = 0.002). Conclusions Considerable prevalence of autoimmune conditions in relatives of people with AD confirms substantial risk of autoimmunity, especially in females and relatives of patients affected by multiplex autoimmunity. Our data corroborate the recommendation of active screening for autoimmune disorders, particularly thyroid disease, among AD family members.