Monoclonal gammopathies can induce clinical or biological symptoms, independent of any associated hemopathy. Cryoglobulins types I and II are responsible for cutaneous lesions, peripheral neuropathy, and membranoproliferative glomerulopathy. Peripheral neuropathies associated with monoclonal gammopathy are chronic, distal, symmetrical and progressive, in two thirds of the cases the monoclonal component reacts with a neuronal antigen principally myelin associated glycoprotein. POEMS syndrome is characterized by: polyneuropathy, organomegaly, endocrine disorder, monoclonal component, and skin diseases. Deposits of light chains of immunoglobulins are responsible for a glomerulopathy, and sometimes affect other organs (skin, heart). Other manifestations are described: angioneurotic oedema, acquired Willebrand disease, systemic capillary leak syndrome, Fanconi syndrome. Treatment of the gammopathy can control associated affections.