Cutaneous involvement by IgD myeloma.

Multiple, firm, nontender, violaceous, cutaneous and subcutaneous nodules of the abdomen and thighs developed in a 53-year-old man with proven IgD myeloma. A biopsy specimen showed dermal infiltration by large atypical undifferentiated cells similar to those previously found on bone marrow aspiration. Despite intermittent improvement with radiotherapy and chemotherapy, the patient died and an autopsy showed multiple osteolytic lesions and massive involvement with tumors that encased the pelvic organs, infiltrated and replaced portions of the psoas muscles, infiltrated the kidneys and intestines, and replaced the bone marrow by small and intermediate-sized malignant lymphoid cells. IgD myeloma is a rare hematologic malignancy that occurs at a younger age than other forms of myeloma, has a high incidence of involvement of soft tissues, and is a particularly dedifferentiated and vicious form of myeloma.