Specific histopathological features include papillary edema, angiocentric and reticular dermal lymphohistiocytic infiltrate, as well as features reminiscent of lupus, such as interface dermatitis and degeneration of the dermo-epidermal junction with deposition of immunoglobulins (IgM, IgA) and complement (C3). The gene discussed is C3; the disease is systemic lupus erythematosus.