Controversies in chronic histiocytic intervillositis

Understanding the“paradox” of pregnancy remains a challenging field of investigation especially when immunological dysregulation is suspected in pathological pregnancies. Chronic histiocytic intervillositis (CHI) is an example of a rare placental inflammatory disease that can occur during any trimester of pregnancy. The pathogenesis of CHI involves an abnormal immune response characterized by an inflammatory infiltrate of maternal CD68+ mononuclear immune cells in the intervillous space. CHI may be associated with villous and intervillous fibrinoid deposits. The precise immunological mechanism is not yet fully understood; it probably relies on an allo-immune of graft rejection rather than an auto-immune mechanism, although it has been described in several autoimmune diseases. CHI has also been described in COVID19 infected pregnant women. The recurrence rate is high and complications are severe: CHI is strongly associated with fetal growth restriction, miscarriage and stillbirth. The management of these patients remains an issue lacking of -standardized guidelines. The aim of this narrative review is to focus on the knowledge, pathogenesis, diagnosis and treatment of CHI over the last 5 years.