Cutaneous Multiple Myeloma.

Multiple myeloma is a plasma cell dyscrasia characterized by abnormal bone marrow clonal plasma cells, histological confirmation of plasmacytoma, monoclonal protein in serum or urine, and evidence of end-organ damage. Organ involvement in multiple myeloma manifests as CRAB (hyperCalcemia, Renal insufficiency, Anemia, lytic Bone lesions). Cutaneous complications in multiple myeloma have been reported in many different phenotypes such as cryoglobulinemia rash, bruising, amyloid deposition, and squamous cell carcinoma. However, cutaneous metastasis of multiple myeloma is very rare with fewer than 100 cases described in the literature so far. Here, we present a case of biopsy-confirmed primary cutaneous multiple myeloma. Our case has other less common features of multiple myeloma such as renal amyloidosis and a coexisting malignant melanoma. This case report describes a unique presentation of multiple myeloma to understand the disease better.