An outbreak of thyrotoxicosis due to atypical subacute thyroiditis

We describe an epidemic of self-limited (6 weeks) thyrotoxicosis which affected 12 index cases, 5 household contacts, and 6 retrospectively identified cases in July, August, and September, 1987 in the town of Winterswijk (28,011 inhabitants), The Netherlands. A small goiter was present in 9 of the 12 index patients, tender upon palpation in only 2. Signs and symptoms of thyrotoxicosis were accompanied by a low grade fever in combination with fatigue, headache, myalgia, and a fine desquamation of the palms and soles. The apparent incubation time between family members was 6 days. Thyroid technetium uptake was decreased in 10 of 11 tested patients. Laboratory findings included elevated sedimentation rates (up to 68 mm/h), increased liver enzymes, lymphopenia in 2 patients, and absence of thyroid autoantibodies. HLA-B35, associated with classical subacute thyroiditis, was found in 1 patient only. An etiological agent was not identified. No evidence was found for thyrotoxicosis factitia. After 10 months, all patients were euthyroid, without a goiter or thyroid autoantibodies. Thus, a new variant of thyroiditis, atypical subacute thyroiditis, was probably the cause of this unusual outbreak. It is unclear at present if this variant of thyroiditis is common in communities and represents a separate disease entity.