Multiple myeloma causing interstitial pulmonary infiltrates and soft-tissue plasmacytoma

Multiple Myeloma (MM) is a relatively rare disease and MM presenting outside the bone marrow, known as extramedullary myeloma (EMM), is rarer still. While the liver and CNS are most commonly affected in EMM, the lung parenchyma is an especially unusual site of involvement. We present the case of a 64-year-old male with known history of MM admitted with acute respiratory failure and a chest wall mass. Chest CT revealed patchy interstitial and alveolar opacities with no pulmonary masses or nodules. Bronchoalveolar lavage (BAL) was performed, with flow cytometry demonstrating monoclonal plasma cells expressing CD38, CD138 and CD56 with lambda light chain restriction. Fine Needle Aspiration of chest wall mass revealed CD138-positive cells as well. Review of the literature revealed only one other documented case of a patient presenting with both interstitial lung parenchymal involvement with MM as well as soft tissue plasmacytoma, with this occurring in a patient who had previously underwent stem cell transplant. To our knowledge, we report the first recorded case of this presentation in a patient without a history of stem cell transplantation. Furthermore, it demonstrates the utility of using BAL, rather than lung biopsy, to establish the diagnosis through less invasive means.