In our North American study population, 10.2% of patients reported a history of AITD compared with only 5.4% in the control population (data not shown; noteworthy, of the healthy controls with a personal history of AITD, all had a family history of autoimmune bullous disease, mainly PV), but a higher number of patients had serum reactivity to autoantibodies classically related to AITD (13.9% anti-TPO and 6.8% anti-Tg reactivity). Here, TPO is linked to acquired polycythemia vera.