Placental Mesenchymal Dysplasia: Ultrasound Characteristics and Diagnostic Pitfalls.

Placental mesenchymal dysplasia (PMD) is a rare, benign developmental anomaly with a reported prevalence of 0.02% (Arizawa and Nakayama, 2002). It is characterized by placentomegaly with multiple cystic lesions of the stem villi and vascular anomalies (Pawoo and Heller, 2014). Early detection of PMD has been described during routine prenatal ultrasound (Vaisbuch et al., 2009). The sonographic characteristics of PMD include increased placental thickness and multiple cystic areas within the placenta with either an absence of blood flow or with low venous Doppler signals (Vaisbuch et al., 2009). The differential diagnosis of multicystic placental lesions with the presence of a live fetus include partial molar pregnancy, multiple hematomas, chorioangioma Beckwith-Wiedemann syndrome and PMD. Chorioangiomas are well circumscribed masses within the placenta and they are characterized by the presence of a single feeding vessel with the same pulse rate as the umbilical cord (Zalel et al., 2002). Invasive prenatal testing is required for the exclusion of partial molar pregnancy and Beckwith-Wiedemann Syndrome (Vaisbuch et al., 2009). Definitive diagnosis of PMD is based on the pathologic examination of the placenta. Histology reveals aneurysm or dilated blood vessels that may be thrombosed. The stem villi are edematous and enlarged with thick-walled vessels, without trophoblastic proliferation (Pawoo and Heller, 2014). This case report highlights the significance of the early detection of PMD, illustrates the pitfalls in differential diagnosis and provides valuable insights regarding PMD management in a clinical setting.