The true incidence of placental mesenchymal dysplasia

摘要

We read with interest the article by Zeng et al. on the incidence of placental mesenchymal dysplasia (PMD) in a normal population (1). Over a period of 18 years, they could identify only two cases amongst over 95 000 deliveries at their institution and calculated the rate to be as low as 0.02 per 1000 deliveries.Placental mesenchymal dysplasia is an extremely rare occurrence. The diagnosis is suspected sonographically and confirmed histopathologically. Sonographic findings of PMD are a thickened placenta with hypoechoic areas (2). Histopathologically, PMD placentas are large for gestational age, with aneurysmally dilated chori-onic plate vessels, cystically dilated vesicles and fibromuscular hy-perplasia (2). On microscopic examination, dilated stem vessels with thickened vasculature surrounded by normal villi and lack of tro-phoblastic proliferation are obvious. The diagnosis of PMD is generally one of exclusion, with differential diagnoses such as complete molar pregnancy with co-twin, partial molar pregnancy and chorioangioma being more common in clinical practice.