[Characteristics and clinical course of patients with subacute thyroiditis without typical signs and symptoms]

To determine the characteristics and clinical course of patients with subacute thyroiditis (SAT) without typical signs and symptoms, clinical and pathologic records of the patients were reviewed and compared with those of patients with typical SAT. During the past 10 years, 11 of 105 patients with SAT did not have enough typical features for a diagnosis of SAT (atypical SAT). They included one male and 10 females with the average age of 50 years. The incidence of neck pain as the initial symptom in the patients with atypical SAT was low (18%) compared with that in the patients with typical SAT (69%). Of the patients with atypical SAT, 42% had elevated thyroid hormone levels and 46% had suppressed TSH levels, whereas the percentages in the patients with typical SAT were 76% and 85% respectively. Nine of 11 patients were misdiagnosed as having papillary carcinoma by physical examination, and 4 by ultrasonography. However, aspiration cytology could make a precise diagnosis of SAT in 4 patients at the time of clinical diagnosis and 3 other patients after reevaluation. Eight patients were admitted to the hospital under the diagnosis of thyroid cancer and 4 underwent surgical resection. Differential diagnosis between atypical SAT and papillary carcinoma is important, and aspiration cytology could be a conclusive diagnostic tool to avoid unnecessary treatment.