Monoclonal immunoglobulin may cause various skin manifestations. The aim of this article is to remind us of situations, in which a dermatology specialist should think about a possible relationship with blood diseases, investigate the presence of monoclonal immunoglobulin and alternatively send the patient to a respective hematology department. In the article we describe cryoglobulinemia, symptoms of monoclonal immunoglobulin IgA type binding to skin structures, urticarial manifestations of Schnitzler's syndrome, scleredema in monoclonal gammopathy and show pictures of our patients, in whom we diagnosed and treated these skin complications.