CTLA4 and systemic lupus erythematosus: In this regard, it was shown that CTLA-4 gene polymorphisms significantly influence the risk of autoimmune diseases, including Graves' disease, systemic lupus erythematosus, autoimmune hypothyroidism, celiac disease, Henoch-Schönlein purpura, type-1 diabetes [11–13], and BD [3], in many cohorts although this has not been studied in Egyptian BD.