Peculiarities of Graves' disease in children and adolescents with Down's syndrome.

Objective: To compare the presentation and clinical course of Graves’ disease (GD) in two pediatric populations consisting of 28 patients with Down’s syndrome (DS) and 109 controls without DS respectively. Design and methods: The evolution over time of GD was determined in both groups according to the clinical changes and the variations in TSH, free thyroxine, and TSH receptor autoantibodies serum levels during the entire follow-up. Results: Female prevalence (50 vs 81.6%; c2Z12.0, P!0.0005) and average age at GD presentation (9.9G4.4 vs 11.5G3.5 years, P!0.05) were significantly lower in DS group than in controls. Clinical responsiveness to methimazole therapy was significantly better in DS patients, as demonstrated by both the lower relapse rates after the first cycle withdrawal (7.1 vs 31.2%; c2Z7.4, P!0.005) and the higher persistent remission rates after definitive therapy withdrawal (46.4 vs 26.7%; c2Z4.1, P!0.05). Moreover, in DS group, no patients needed surgery or radioiodine ablation, whereas nonpharmacological treatment was necessary in 11% of controls (c2Z3.8, P!0.05). Antecedents of Hashimoto’s thyroiditis (HT) were documented in 21.4% of DS patients and in 3.7% of controls (c2Z10.4, P!0.005). Association with other autoimmune diseases was detected in 32.1% of DS cases and in 12.8% of controls (c2Z5.94, P!0.025). Conclusions: GD in DS children and adolescents is characterized by several peculiarities: i) earlier presentation; ii) no gender predominance; iii) less severe clinical course; iv) higher frequency of documented HT antecedents; v) more frequent association with other autoimmune diseases.