An adult Caucasian female developed a previously unreported association of pelvic endometriosis (PE) with the triad of alopecia universalis (AU), autoimmune thyroiditis (AT) and multiple sclerosis (MS). Molecular human leukocyte antigen (HLA)-tissue typing of this subject showed the presence of the DR(2) 15 and DR(3) 17 alleles, which are associated to an increased risk of MS and AT, respectively. Clinical onset of AT followed withdrawal of corticosteroid treatment for AU, whereas MS become clinically evident after withdrawal from long-term estroprogestin therapy for PE. This clinical case is presented to discuss the autoimmune origin of PE, its possible association with multiple autoimmune disorders as well as the effect of other factors, such as administration and/ or discontinuation of specific hormonal regimens, on genetic autoimmunity-prone background.