We report on a 54-year-old patient with an 11-year history of Arndt-Gottron scleromyxoedema. We found typical lichenoid papules, diffuse skin thickening and skin hardening. Clinical and laboratory investigations revealed a monoclonal gammopathy of the IgG1 type, normal histology of the bone marrow and normal urine. Therefore, a diagnosis of monoclonal gammopathy of undetermined significance was recorded. Phimosis and stenosis of the urethra were the only other pathologic findings. Systemic treatment with chlorambucil and PUVA had little beneficial effect on the skin thickening after 9 months.