Hashitoxicosis in children: clinical features and natural history.

Objective: To determine the incidence, natural history, and clinical characteristics of Hashitoxicosis (Htx) in pediatric patients with autoimmune thyroiditis.

Study Design: Medical records of children diagnosed with Hashimoto thyroiditis between 1993 and 2002 were reviewed. The clinical course of patients presenting with hyperthyroidism was determined. Variables including sex, age, family history, thyroid hormone levels, anti-thyroid antibody titers, 123 I thyroid scan results, and presenting features were investigated as possible predisposing factors for the development of Htx.

Results: Out of 69 patients with autoimmune thyroiditis, 8 were diagnosed with Htx. The duration of hyperthyroidism ranged from 31 to 168 days. Three patients became hypothyroid after an average of 46.3 +/- 13.2 days, and 5 patients became euthyroid after an average of 112.8 +/- 59.8 days. Additional findings included an elevated thyroid stimulating immunoglobulin (TSI) titer in 3 of the 8 patients with Htx, and increased uptake on 123 I scan in 2 patients.

Conclusion: Htx is an uncommon yet important cause of hyperthyroidism in children that has a variable clinical course. The diagnosis may be complicated, as presenting features sometimes exhibit significant overlap with Graves' disease. No factors predisposing to the development of Htx were identified.