Chronic Histiocystic Intervillositis (CHI)
How common is CHI?
It is considered a rare placental inflammatory disease. Currently diagnosed in approximately 1% of spontaneous abortions/miscarriages and in less than 1% of placentas in 2nd and 3rd trimester. It is frequently missed as a diagnosis with a high recurrence risk as placentas may not always be analysed after an event. The same applies for cases of fetal growth restriction with live birth outcome. Furthermore, there is still lack of awareness among Pathologists themselves who are still being educated on how to recognise it when analysing the placenta.
What Causes CHI?
At this current time the trigger is unknown, possible immunologic origin, most likely alloimmune due to the nature of the disorder. CHI might also be confused with infectious placental lesions observed in; malaria, listeriosis, tularemia, CMV, herpes, and polymorphous inflammatory infiltrate.
Women with this problem make antibodies to DNA components in the embryo, or in the pregnancy tissue that surrounds it. These antibodies form first in the blood and later graduate to the lymphatic system and the tissue. After repeated losses, antibodies to DNA components can develop into antibodies that occupy organs such as the uterus, and cause local inflammation that may contribute to further pregnancy losses. For CHI sufferers this manifestation of where antibodies to the baby and components of placental DNA cause inflammation in the placenta.
There is also an association with an abnormal thrombophilia most commonly with Factor V Leiden.