A case of Graves' disease in association with hemiagenesis of the thyroid gland.

Hemiagenesis of the thyroid gland is a rare anomaly. Few cases have been reported in the world literature. We present a case of Graves' disease in association with hemiagenesis of the thyroid gland. In this case, preoperative diagnosis was difficult because of the marked hyperplasia of the single thyroid lobe and the isthmus. Preoperative diagnosis of this anomaly is important to avoid unnecessary exploration of the side where the thyroid lobe is absent and to plan for the extent of thyroid tissue excision to avoid postoperative hypothyroidism. An ultrasound scan of the neck would have been helpful in this case.