The Authors describe the case of a woman affected by generalized plane xanthoma and IgG multiple myeloma with k type immunoglobulins. The association between the two affections is well known. The antilipoprotein activity of the paraprotein has been proved in some cases, associated or not to hyperlipemia. The pathogenetic mechanism of plane xanthoma formation is described briefly. The possible occurrence of plane xanthoma with multiple myeloma is stressed, along with the possible association with other systemic diseases.