Peculiarities of Presentation and Evolution over Time of Hashimoto's Thyroiditis in Children and Adolescents with Down's Syndrome

Background: Studies concerning presentation and evolution over time of Hashimoto's thyroiditis (HT) in children with Down's syndrome (DS) are few, are based on limited study populations and do not include control HT groups without DS. The aim of this multicenter study was to shed further light on the relationships between DS and HT in childhood.

Design: In this retrospective study we compared thyroid function patterns at HT presentation in 2 groups of children with (group A) or without DS (group B), including 146 and 553 cases, respectively. All group A patients were subsequently re-examined after a median interval of 5.1 years in order to prospectively re-evaluate the evolution over time of thyroid function patterns in DS.

Results: In group A, female predominance, age at HT diagnosis and rates of familiarity for thyroid diseases were significantly lower than in group B, whilst the association with non-thyroidal autoimmune diseases was more frequent. The hormonal patterns that were most frequently found in the 2 groups were, respectively, subclinical hypothyroidism (in group A) and euthyroidism (in group B). Thyroid dysfunctions were, overall, more frequent in group A (86.3 vs 45.7%, p<0.001). At re-evaluation, DS children exhibited further deterioration of thyroid function with some cases switching towards Graves' disease (GD).

Conclusions: HT in DS children: a) presents earlier, is not associated with female predominance and is more frequently associated with other autoimmune diseases; b) presents only very infrequently with a euthyroid hormonal profile; c) in a limited rate of cases switches with time to GD.