COL17A1 and autoimmune disease: Consistent with the improvement in BP symptoms, AFVI symptoms also improved, suggesting a link between BP and AFVI based on the presence of IgG4 and possible sequence homology between BP180 protein and factor V. In conclusion, clotting-related tests, including factor V tests, should be performed if coagulation disorders persist during the treatment of autoimmune diseases such as BP or infectious diseases.