Progesterones are frequently used to treat endometriosis. Exaggerated response of the endometrium to high levels of progesterone can result in a decidualization reaction. Decidualization may cause an exacerbation of symptoms of dysmenorrhea associated with endometriosis.
A 16-year-old girl with uterine didelphys and obstructed hemivagina presented with irregular bleeding and severe abdominal cramping after resection of the vaginal septum. Persistent endometriosis treated with norethindrone acetate resulted in severe colicky abdominal pain and expulsion of a decidual cast.
Membranous dysmenorrhea can occur in response to excess progesterones. An understanding of the physiologic response of the endometrium to treatment will guide us to a high clinical suspicion of this rare entity when symptoms worsen in response to progesteronal treatment for endometriosis.