Studies on a patient with leucocytoclastic vasculitis ‘pyoderma gangrenosum’ and paraproteinaemia

A patient with leucocytoclastic vasculitis, pyoderma gangrenosum, chronic pyelonephritis and a paraprotein of IgA type is described. The vasculitis responded favourably to dapsone therapy, while the pyoderma gangrenosum improved only when steroids were also given. During an exacerbation following withdrawal of dapsone, the serum IgG level fell early, but the β1c globulin level remained normal. Immunofluorescence studies on a vasculitic lesion showed granular deposits of IgG and β1c the walls of the blood vessels and a more extensive exudate of fibrin. Skin testing with bacterial antigens and patch testing to potassium iodide produced lesions which clinically, histologically and immunologically resembled the spontaneous vasculitic lesion.