Microchimerism and thyroid disorders: current knowledge and future prospects

This review will provide an overview of a novel phenomenon in medicine and endocrinology known as microchimerism (MC). MC is defined as the long-term presence of genetically distinct populations of cells in peripheral blood and tissues of individual. This condition may be caused by the transplacental bidirectional cell trafficking between mother and fetus during pregnancy. Other sources are the passage from a twin or a vanished twin and iatrogenic interventions such as organ transplantation and blood transfusion. Long-term consequences of MC and its influence on woman's health are under active investigation. Recent studies have shown a broad spectrum of its biological effects either beneficial or adverse. MC has been suggested to play a key role in the pathogenesis of autoimmune diseases. It is assumed that microchi-meric cells could initiate a "graft versus host" or "host versus graft" reactions. MC has been extensively studied in autoimmune thyroid diseases (AITD). MC could explain the higher prevalence of AITD in females and frequent manifestation during the postpartum period. It is proposed that microchimeric cells could reduce the risk of cancer development and be a part of tissue repair. MC has also been investigated in papillary thyroid cancer. Further studies of this phenomenon are mandatory to get more insights about its role in thyroid cancer and AITD development. This could provide novel therapeutic, preventive or prognostic perspectives regarding these diseases.