The association of two or more autoimmune disorders in the same individual has been attributed to "shared autoimmunity" caused by the interaction between genetic and environmental factors. We present the retrospective analysis of 56 patients with Immune Thrombocytopenia (ITP) associated with other autoimmune disorders. Age, sex, clinical manifestations, platelet count, platelet autoantibodies and therapeutic responses were similar to those described in isolated ITP. However, we found a higher proportion of familial forms, suggesting a greater proportion of genetics in the etiopathogenesis of ITP associated with other autoimmune disorders. A total of 71 associated autoimmune disorders were found, the most frequent being systemic lupus erythematosus and Hashimoto thyroiditis. Most autoimmune disorders appeared before or after ITP but their simultaneous presentation was less frequent. Isolated laboratory markers of additional auto-immune disorders, mainly antinuclear and antithyroid antibodies, were found in about 20% of patients. Unlike ITP secondary to infectious or neoplastic diseases, ITP associated with other autoimmune disorders did not show significant differences with isolated ITP and it could appear indistinctly before, simultaneously, or after the associated disease. These characteristics suggest the need for a critical reconsideration of the term "secondary ITP" when ITP is associated with other autoimmune disorders.

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