[Atypical subacute thyroiditis in combination with Grave's disease:Diagnostic difficulties in a case report].

Subacute thyroiditis is a common inflammatory disorder of the thyroid gland, possibly of viral etiology, that typically presents with neck pain, fever and tenderness on palpation of the thyroid gland. Graves' disease is an autoimmune thyroid disorder caused by stimulation of the thyroid gland by thyrotropin receptor antibodies (TRAb). The development of Graves´ disease and subacute thyroiditis simultaneously is an uncommon condition and only a few cases have been reported. In this article we present a case of a 46-year old woman diagnosed with Graves´ disease who was started on thiamazole and weeks later developed high fever. Several differential diagnoses were considered such as infection, lymphoma and vasculitis due to thiamazole. Finally, the fine needle aspiration of the thyroid gland displayed histopathological features of subacute thyroiditis. Remarkably, our patient did not have neck pain or tenderness on palpation of the thyroid gland and overall the clinical presentation of subacute thyroiditis was atypical. Thus, subacute thyroiditis may be considered as a potential cause of fever of unknown origin.