Placental mesenchymal dysplasia (PMD) is a rare, benign condition that is characterized by enlargement of the placenta with multiple bunches of grape-like vesicles that can resemble a molar pregnancy by ultrasound and gross pathologic examination.
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Epidemiology
This is an often underdiagnosed and underreported case due to lack of awareness. It has been documented to be more in female fetuses with an F:M of ~3.5:1.
Clinical presentation
Clinical presentation is diverse and non-specific
- uneventful pregnancy with postnatal pathologic findings of PMD
- incidental ultrasonographic abnormalities of the placenta
- elevated maternal serum alpha-fetoprotein concentrations
- fetal growth restriction
- fetal demise
- vaginal bleeding
- preterm delivery
Associations
- fetal anomalies (e.g. fetal liver cysts or vascular malformations)
- fetal overgrowth with Beckwith-Wiedemann syndrome (BWS) features (placentomegaly, omphalocoele, macroglossia and visceromegaly)
Radiographic features
Ultrasound
The placenta is thickened with multiple cystic or hypoechoic areas. Doppler findings are variable. There are many documented cases of no vascularity within the lesion and further development of vascularity within. These changes could be due to progressive dilatation of chorionic arteries and veins that become aneurysmal.
MRI
One study showed that MRI could help differentiate between complete hydatidiform mole with coexistent fetus (CHMCF) by demonstrating PMD as multicystic lesions within the placenta of the fetal sac, and CHMCF with multicystic lesions located within an extra fetal sac 4.
Treatment and prognosis
The outcome of the fetus is variable ranging from a completely normal fetus to an increased risk of IUGR or fetal demise.
History and etymology
It was first described in 1991 by Moscoso et al.
Differential diagnosis
Possible differential considerations include
- partial molar pregnancy
- hydropic degeneration of the placenta
- complete hydatidiform mole with coexistant fetus (CHMCF)
- chorioangioma
- subchorionic hematoma
- placental infarcts
- spontaneous abortion with hydropic changes
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