Abstract
BACKGROUND: Limited awareness of placental mesenchymal dysplasia (PMD) and the diagnostic challenges in differentiating it from partial hydatidiform moles on imaging often lead to inappropriate management. This study presents a case report and literature review to elucidate the etiology, clinical features, and management of PMD. CASE PRESENTATION: The patient was admitted with a history of amenorrhea lasting over two months and experiencing vaginal bleeding for four days. Ultrasonography at 12 weeks of gestation revealed extensive cystic changes within the placenta, and was subsequently corroborated by magnetic resonance imaging. The differential diagnosis comprised placental structural abnormalities indicative of PMD or a hydatidiform mole. The patient opted to terminate the pregnancy citing concerns regarding an unfavorable prognosis. Placental pathology confirmed PMD. Fetal short tandem repeat analysis revealed a biparental diploid, whereas the placenta demonstrated androgenetic and biparental chimerism. Postoperative serial monitoring indicated a progressive decrease in serum β-hCG level, and no signs of gestational trophoblastic disease or other maternal complications were observed. CONCLUSION: PMD should be considered when prenatal ultrasonography reveals cystic placental lesions, typically manifested as cystic or hypoechoic regions within an enlarged placenta and often accompanied by mildly elevated maternal serum β-hCG levels. The fetal karyotype is typically normal, with a predominance of females. Pathological examination demonstrates a considerably enlarged placenta characterized by vesicular, grape-like structures on its surface. Some mothers may develop complications such as hypertensive disorders of pregnancy, while adverse perinatal outcomes-such as preterm delivery or stillbirth due to fetal distress or malformations-may also occur. However, a considerable proportion of maternal and fetal outcomes remains favorable. Enhanced maternal and fetal monitoring in PMD pregnancies has the potential to enhance perinatal outcomes.