The association of acquired hemophilia A with bullous pemphigoid is probably due to a cross-reaction of autoantibodies because of sequence homology between FVIII epitopes and the collagen XVII domain (BP180), a key component of the epidermal anchoring complex, which is also involved in the regulation of keratinocyte differentiation [4]. The gene discussed is COL17A1; the disease is bullous pemphigoid.