Increased risk for type I (insulin-dependent) diabetes in relatives of patients with alopecia areata (AA).

The prevalence of various chronic diseases was compared in 517 individuals with alopecia areata, and 2,969 of their first degree relatives. As previous reports have suggested an increased incidence of diabetes in relatives of patients with alopecia areata, special attention was given to the prevalence of Type 1 and Type 2 diabetes in the patients and in their relatives. Several immunologic diseases were increased in alopecia probands and relatives. Thyroid disease, vitiligo, Addison disease, and pernicious anemia were more prevalent in probands and in their relatives than in the general population. Specifically, a high rate of thyroid disease was found in probands (14.7%) and in their first degree relatives (4.2%). Only one proband had Type 1 diabetes, yet there were 14 sibs with Type 1 diabetes. Thus, Type 1 diabetes was significantly more prevalent in the sibs (1.2%) than in either the probands with alopecia (0.2%), or the general population (0.12-0.25%) (P < 0.05)). In contrast, Type 2 diabetes was not more common in probands or in sibs than in the general population. These data suggest that alopecia areata protects against Type 1 diabetes in predisposed individuals. The high rate of thyroid disease suggests that screening probands and first degree relatives for thyroid disease should be considered.