Placental mesenchymal dysplasia: A rare case report and literature review

RATIONALE: Placental mesenchymal dysplasia (PMD) is a rare placental disorder that poses diagnostic challenges and is often misdiagnosed as a trophoblastic tumor. While PMD is associated with fetal growth restriction, intrauterine fetal death, and pregnancy-induced hypertension, it does not involve malignant trophoblastic disease. Accurate diagnosis is crucial for optimizing maternal and fetal outcomes. PATIENT CONCERNS: A 30-year-old female, gravida 3, para 1, with an uncomplicated medical history, presented with early pregnancy bleeding, which was managed with oral progesterone. Ultrasound at 13 weeks showed normal fetal morphology but a honeycomb-like placental appearance. At 23 weeks, ultrasound revealed fetal growth restriction, thickening of the placenta, and abnormal umbilical artery flow. Magnetic resonance imaging at 32 weeks confirmed abnormal placental masses. DIAGNOSES: Ultrasound, magnetic resonance imaging, and genetic testing (noninvasive prenatal testing, amniocentesis, and chromosomal microarray analysis) confirmed normal karyotype and identified distinctive placental abnormalities. Histopathological examination revealed edematous villi, fibromuscular hyperplasia, and amyloid-like protein deposits, consistent with PMD. INTERVENTIONS: Prenatal care included enoxaparin sodium and management of fetal distress at 32 weeks with a cesarean section. Magnesium sulfate and dexamethasone were administered for fetal protection. OUTCOMES: Both mother and infant were healthy postpartum. The infant had favorable Apgar scores, and the patient's blood pressure was managed with antihypertensive therapy. Maternal β-human chorionic gonadotropin levels remained normal throughout the pregnancy and postpartum. LESSONS: PMD is an exceptionally rare placental disorder with a low incidence. It often presents with atypical ultrasound findings and can easily be misdiagnosed as a trophoblastic tumor, leading to unnecessary interventions. Diagnosing PMD is challenging, particularly in the absence of specific clinical symptoms. Clinicians must enhance awareness of this rare condition, prioritize early and accurate diagnosis through advanced imaging and histopathology, and differentiate PMD from other placental pathologies to ensure appropriate management and improve maternal-fetal outcomes.