Plasma concentrations of complement-modulating proteins (C1 inhibitor, C4 binding protein, factor H and factor I) in inflammatory dermatoses with special reference to psoriasis.

By using single radial immunodiffusion, plasma levels of four complement-modulating proteins, i.e. C1 inhibitor (C1INH), C4-binding protein (C4bp), factor H and factor I were measured in 42 psoriatic patients and in 60 patients with other inflammatory skin diseases in comparison with 27 normal controls. In psoriatic patients and those with related pustular dermatoses, the levels of C4bp, factor H and factor I were significantly increased. They correlated well with both extent of skin changes and disease activity. In contrast, in nonpsoriatic inflammatory dermatoses only factor H values were significantly increased in toxic erythema and factor I in atopic dermatitis. These results offer additional support for the hypothesis that the complement system is involved in psoriasis and related sterile pustular dermatoses.