Spontaneous ovarian hyperstimulation in a nonpregnant woman with PCOS: a rare case highlighting FMN2 missense mutation and androgen receptor gene deletion.

backgroundPolycystic ovary syndrome (PCOS) is a common endocrine disorder characterized by oligo-anovulation, hyperandrogenism, and polycystic ovarian morphology. While its etiology is multifactorial, genetic susceptibility plays a key role in its pathophysiology. CASE PRESENTATION: We report a rare case of spontaneous ovarian hyperstimulation syndrome (sOHSS) in a 26-year-old nulligravid Japanese woman with PCOS who had never received exogenous gonadotropins. She presented with amenorrhea, elevated luteinizing hormone (LH), and bilaterally enlarged ovaries mimicking OHSS. Laparoscopic ovarian drilling (LOD) was performed, resulting in marked LH reduction, restoration of ovulatory cycles, and spontaneous pregnancy. Genetic analysis revealed a novel heterozygous missense mutation in the FMN2 gene (c.3461 C > T, p.Pro1154Leu) and a heterozygous deletion in exon 1 of the androgen receptor (AR) gene, detected in peripheral blood, bilateral ovarian tissue, and granulosa cells. No mutations commonly associated with PCOS or OHSS were found. During pregnancy, bilateral ovarian enlargement progressed, and at 33 weeks, magnetic resonance imaging revealed ovarian herniation into the pouch of Douglas. Due to concern relating to a possible mechanical dystocia, an elective cesarean delivery was performed at 38 weeks, resulting in the birth of a healthy infant.

conclusionThis is the first report identifying FMN2 and AR gene variants in a patient with sOHSS and PCOS, suggesting that noncanonical rare mutations may underlie atypical phenotypes and contribute to ovarian dysfunction in the absence of exogenous stimulation.