Cutaneous manifestations of multiple myeloma.

We report the cutaneous manifestations of multiple myeloma, using a retrospective review of 115 patients' records obtained from tumor registry files. Five patients were found to have biopsy-proved extramedullary plasmacytomas without extension from an underlying bony focus. Twelve patients had ecchymoses without thrombocytopenia; two of them had biopsy-proved amyloidosis. One patient presented with pyoderma gangrenosum and was subsequently diagnosed with multiple myeloma. The last patient initially presented with what clinically appeared to be leukocytoclastic vasculitis, and, in the course of a standard workup, he was diagnosed with multiple myeloma. These findings are discussed with regard to the current literature on the cutaneous manifestations of multiple myeloma.