RESUMEN
Since the mid 1900s, a significant increase of infectious, hematological, and autoimmune diseases has been reported in patients with Down's syndrome (DS), independent of sex, age, family history, and exposure to other risk factors, suggesting an intrinsic alteration of the immune system. Several in vitro and in vivo studies have demonstrated alterations of both cellular and humoral immunological response mainly, although not exclusively, secondary to alterations of the expression of autoimmune regulator gene (located on chromosome 21), leading to thymic structural and functional impairments. Autoimmune thyroid disorders (i.e. Hashimoto's thyroiditis and Graves' disease) and type 1 diabetes mellitus are the most common autoimmune endocrine disorders associated with DS, and present with some peculiar features. The underlying etiopathogenic mechanisms and clinical significance of some mild laboratory alterations are still poorly understood. For these aspects, together with the associated multiple comorbidities and intellectual impairment - that make DS patients dependent on care givers - and in the absence of definite guidelines, disease management is very challenging and should be patient-tailored.