Placental mesenchymal dysplasia is a benign condition that can be confused with a molar pregnancy by ultrasound scanning and gross examination. Conservative management should be considered with a normal-appearing singleton fetus and a cystic-appearing placenta. We present a case of placental mesenchymal dysplasia with a favorable outcome.
Placental mesenchymal dysplasia (PMD) is a rare benign condition that is characterized by placentomegaly and grapelike vesicles that can resemble a molar pregnancy by ultrasound and gross placental examination. PMD was described initially by Moscoso et al as stem villous hyperplasia with elevated maternal serum alpha-feto-protein and enlarged placentas with ultrasound features that are suggestive of partial mole. PMD should be included in the differential for a cystic-appearing placenta with a normal fetus. Herein, we describe a case of PMD with emphasis on sonographic findings and pathologic correlation.
Case Report
A 21-year-old woman (3 pregnancies; 0111 [para: 0 term delivery, 1 preterm delivery, 1 abortion, 1 living] viable births) with a normal-appearing fetus and an abnormal-appearing cystic placenta on ultrasound scanning was transferred at 19 weeks to the Maternal Fetal Medicine clinic. The patient had a normal sequential screening, except for an elevated alpha-feto-protein (multiples of the median, 5.4; human chorionic gonadotropin [HCG] multiples of the median, 6.95), a normal fetal karyotype (46 mIU/mL), and an elevated β-HCG level of 167402. A chest x-ray, liver enzyme levels, and renal laboratory values were normal. The thyrotropin level indicated hyperthyroidism, which was treated with propothiouracil.
The differential diagnosis included a complete molar pregnancy with co-twin, a partial molar pregnancy, a chorioangioma, or PMD. The patient elected to continue the pregnancy and accepted the increased risk of preeclampsia (27%), persistent gestational trophoblastic disease (GTD; 45%), fetal loss (62%), and maternal morbidity. At 24, 28, and 32 weeks’ gestation ( Figure 1 ) , the placenta continued to be large and hydropic by ultrasound scanning. Throughout the pregnancy, the fetal growth curves were normal. Gestational hypertension was diagnosed with a normal 24-hour urine test (150 mg) with elevated blood pressures 6 hours apart along with normal laboratory values at 32 weeks’ gestation.
The patient then returned at 33 weeks’ gestation in preterm labor (9 cm) and within 1 hour delivered a viable female infant (1802 g; 40%), with Apgar scores of 4 and 7. The placenta appeared grossly large with hydropic villi ( Figure 2 ) . Evaluation of the infant by the neonatal team was normal. The patient recovered normally and was discharged home on postpartum day 2. The B-HCG decreased 2 weeks after the delivery to 113 mIU/mL, but the patient was then lost to follow-up evaluation.
