Factor VIII related antigen in connective tissue disease patients and relatives.

This study assayed serum levels of FVIII Rag as a marker of endothelial injury in patients not only with frank connective tissue disease but also in those presenting with Raynaud's phenomenon and in families of those with systemic sclerosis. Elevated levels of FVIII Rag were found in 62% of patients with systemic sclerosis (SS), 38% with systemic lupus erythematosus (SLE), 67% with mixed connective tissue disease (MCTD) and in 17% with primary Raynaud's phenomenon. Twenty per cent of first degree relatives of patients with SS also demonstrated high levels of FVIII Rag and certain antibodies, namely those reacting with U1RNP and the centromere. The association between elevated FVIII Rag and antibodies linked to Raynaud's and vasculitis lends support to antibody involvement in pathogenesis. High levels of FVIII Rag in family members may reflect an increased susceptibility of endothelium to injury particularly since relatives also have a higher frequency of clinical features such as Raynaud's phenomenon.