An 83-year-old man with multiple myeloma presented with anemia and increased immunoglobulin A (IgA) level after chemotherapy. Computed tomography revealed wall thickening in the small intestine, and contrast radiography showed a 3/4-rounded ulcerative lesion in the jejunum. Endoscopic biopsy revealed monoclonal infiltration of IgAκ plasma cells, which resembled the initial pathological finding of bone marrow biopsy, leading to a diagnosis of extramedullary plasmacytoma secondary to multiple myeloma. Although systemic chemotherapy was administered, frequent transfusion of red blood cells was needed because of increased bloody stool until the patient underwent small intestine resection. He died from disease progression of multiple myeloma 7 months after the diagnosis of plasmacytoma in the jejunum.
The incidence of secondary extramedullary plasmacytoma in the small intestine is extremely rare. Although this disease confers poor prognosis, the treatment strategy remains uncertain because of a small number of patients.
