Histological, clinical and laboratory findings of acute exacerbation of Hashimoto's thyroiditis--comparison with those of subacute granulomatous thyroiditis.

As reported previously, acute exacerbation of Hashimoto's thyroiditis shows quite unique histological findings, namely localized edematous inflammation. Similar histological characteristics and clinical manifestations were observed in 7 of 492 patients with Hashimoto's thyroiditis (A group). Their clinical and laboratory findings were compared with those of 15 cases with subacute granulomatous thyroiditis (S group). Age and sex distribution and goiters in A group were 39 +/- 21 years old (mean +/- s.d.), 7/0 (F/M), and 6/1 (diffuse/nodular), respectively. These were somewhat different from those of S group (45 +/- 9, 12/3, and 3/12, respectively). Thyroid functions in A group showed wide variation: 3 cases were euthyroid, 2 were mildly hypothyroid, and one was mildly thyrotoxic and one borderline thyrotoxic, and all of the S group patients were thyrotoxic. Their thyroid radiopertechnetate uptake, scintigraphy, duration from the onset till the first visit, and ESR and CRP values were also different from those of S group. Clinical courses and outcomes of A group were generally favorable, but one of them finally underwent a total thyroidectomy. Per os and intrathyroidal administrations of steroid were effective, but there was observed a recurrence of symptoms in 3 cases. Finally, all 6 cases were left with diffuse goiters, 4 of them remaining euthyroid, and 2 falling into hypothyroidism. The acute exacerbation of Hashimoto's thyroiditis is a rare complication, which is found to be different from subacute thyroiditis on histological, clinical and laboratory findings and is generally subtle. Steroid medication is considered to be the therapeutic choice but careful observation is necessary to avoid a recurrence.