{Reference Type}: Journal Article {Title}: Endometriosis in a 22-Year-Old with Premature Ovarian Insufficiency Secondary to Pre-Pubertal Bone Marrow Transplant: a Case Report. {Author}: Liao C;Ramani S;Parkash V;Kodaman PH; {Journal}: Reprod Sci {Volume}: 0 {Issue}: 0 {Year}: 2024 May 28 {Factor}: 2.924 {DOI}: 10.1007/s43032-024-01601-z {Abstract}: Endometriosis is often diagnosed in reproductive aged women with spontaneous ovarian activity. Here we described a case of endometriosis diagnosed in a patient with premature ovarian insufficiency (POI) due to prepubertal bone marrow transplant (BMT). The patient is a 22-year-old nulligravid female who presented with chronic pelvic pain. She had an inherited bone marrow failure syndrome (Diamond-Blackfan anemia), which required gonadotoxic chemotherapy for BMT at a young age prior to puberty. At age 13, she received hormone therapy with transdermal estrogen with subsequent addition of cyclic progestin and was later transitioned to combined oral contraceptive pills (COC). Endometriosis was suspected due to progressive dysmenorrhea and multiple cyclic systemic symptoms. She underwent a trial of elagolix, but could not tolerate it due to worsened arthralgia. Norethindrone acetate (NET-A) was then started, and she underwent diagnostic laparoscopy. Laparoscopy revealed scattered superficial endometriotic lesions in the pelvis. Histological studies showed florid endometriosis. Patient continues on NET-A 10mg and oral estradiol 0.5mg daily since the surgery and has experienced sustained improvement in her symptoms. Endometriosis should be considered as a possible cause for progressive dysmenorrhea or pelvic pain, even in the setting of POI. The balance between HT for overall health benefits in young women with POI and the risk of endometriosis exacerbation is delicate, but achievable.