Incidence of subacute thyroiditis recurrences after a prolonged latency: 24-year survey.

Subacute thyroiditis, which is considered to be a viral disease, rarely recurs after a complete recovery. We evaluated data on 3,344 patients with subacute thyroiditis who were seen at Ito Hospital between 1970 and 1993. Subacute thyroiditis recurred in 48 of 3,344 patients 14.5 +/- 4.5 yr after the first episode. Five patients experienced a third episode 7.6 +/- 2.4 yr after the second. The mean age of the patients at the first, second, and third episode was 38.4 +/- 6.3, 53.1 +/- 8.9, and 57.8 +/- 10.1 yr old, respectively. The mean incidence of a recurrence was 2.3 +/- 0.9% per year. The erythrocyte sedimentation rate and the duration of treatment were each significantly decreased at the second episode as compared with the first. Thus, recurrences of subacute thyroiditis do occur at least in 2% of patients and exhibited relatively mild clinical manifestations.