Live Births Following IVF-FET in Two Adult Sisters with Nonclassic P450 Oxidoreductase Deficiency: A Case Report Identifying a Novel POR Variant

Background: Cytochrome P450 oxidoreductase deficiency (PORD) is an exceptionally rare form of congenital adrenal hyperplasia (CAH) characterized by impaired activity of multiple microsomal cytochrome P450 enzymes. In adult women, PORD frequently presents with nonspecific reproductive manifestations such as menstrual irregularities, infertility, and ovarian cysts, often mimicking polycystic ovary syndrome (PCOS) or premature ovarian insufficiency (POI). To date, successful pregnancies in affected women remain extremely rare. Case Presentation: We describe two biological sisters with compound heterozygous POR variants c.1811A>G (p.Tyr604Cys) and c.1952_1966del (p.Gly651 _ His655del) , both presenting with infertility and recurrent ovarian cysts but initially misdiagnosed as PCOS or POI. Both exhibited elevated serum progesterone and 17-hydroxyprogesterone (17-OHP) without overt androgen excess, consistent with the paradoxical hormonal signature of PORD. The elder sister underwent a progestin-primed ovarian stimulation (PPOS) protocol, while the younger received a short GnRH agonist protocol; in both cases, a freeze-all strategy was adopted due to supraphysiologic progesterone levels. Subsequent hormone replacement therapy frozen embryo transfer (HRT-FET) combined with glucocorticoid supplementation resulted in singleton live births in both patients. The younger sister developed preeclampsia requiring preterm cesarean delivery, highlighting potential obstetric risks. Conclusion: These cases represent the first report of two siblings with nonclassic PORD achieving live births through IVF-FET. Moreover, we identified a previously unreported POR variant, c.1952_1966del, p.Gly651_His655del, which expands the known mutational spectrum of PORD in the Chinese population. Our findings highlight the importance of early genetic testing in women with atypical infertility, recognition of the distinctive hormonal profile of PORD, and the value of glucocorticoid-supported artificial-cycle frozen embryo transfer as an effective reproductive strategy. Keywords: cytochrome P450 oxidoreductase deficiency, POR gene mutation, infertility, in vitro fertilization, frozen embryo transfer