Dichorionic Twins Discordant for Massive Perivillous Fibrinoid Deposition: Report of a Case and Review of the Literature.

Massive perivillous fibrinoid deposition (MFD) and maternal floor infarction (MFI) are lesions of unknown etiology associated with poor perinatal outcomes, including fetal intrauterine growth restriction and neurodevelopmental injury, high risks of pregnancy loss, and recurrence in subsequent gestations. MFI comprises massive intervillous fibrinoid deposition concentrated at the maternal floor. MFD is a similar lesion but is diffuse within the parenchyma. MFD/MFI lesions represent a spectrum of severity of cloak-like perivillous fibrinoid deposition, and there is mounting evidence that, often, they represent sequelae of immune-mediated phenomena and/or an imbalance in factors that normally maintain the fluidity of blood in the maternal space. There are only a handful of reported instances of discordant MFD/MFI occurrence in twin placentas. We present a fourth such occurrence in a fused, dichorionic diamniotic twin placenta and submit that our dizygotic twin gestation case provides additional supportive evidence that immune-mediated mechanisms are involved in the formation of pathological accumulations of fibrinoid, at least in some cases.