Graves' disease and Hashimoto's thyroiditis are common autoimmune endocrinopathies with a strong familial pattern. However, their mode of inheritance is complex and poorly understood. The striking clinical heterogeneity of these diseases is also an enigma. For example, why do only some patients with Graves' disease develop clinical ophthalmopathy? Why does hyperthyroidism spontaneously remit in about one third of patients with Graves' disease? Why is hypothyroidism in Hashimoto's thyroiditis associated with goiter in some patients, but with thyroid atrophy in others? Why do Graves' disease and Hashimoto's thyroiditis occur in different members of the same family? What determines the heterogeneity of the wide spectrum of antibodies that are detected in autoimmune thyroid disease?
In recent years, powerful new tools have become available to clinical investigators seeking to answer some of these fundamental questions. Among these tools is the ability to determine the haplotype (cluster of alleles) in individual subjects for the