The present disclosure relates to, inter alia, compositions containing an inhibitor of human complement and/or an inhibitor of interferon alpha, and the use of the compositions in methods for treating or preventing Degos' disease in a subject. In some embodiments, the inhibitor is an antibody, or antigen-binding fragment thereof, that binds to a human complement component C5 protein or to a biologically-active fragment of C5 such as C5a or C5b. In some embodiments, the inhibitor is an antibody, or an antigen-binding fragment thereof, that binds to interferon alpha or to an interferon alpha receptor.