Pulmonary Infiltration of Multiple Myeloma Diagnosed by Bronchoalveolar Lavage

Abstract

Background. Multiple myeloma (MM) is a plasma cell neoplasm that can manifest as diffuse pulmonary ground-glass opacities (GGOs) on chest computed tomography (CT), mimicking interstitial or alveolar lung diseases and complicating the diagnosis. Case. A 70-year-old woman presented with progressive malaise, anorexia, back pain, and exertional dyspnea. Laboratory evaluations revealed anemia, thrombocytopenia, hypercalcemia, renal impairment, and serum M-protein positivity. A white blood cell differential count demonstrated abnormalities, prompting the suspicion of a plasma cell disorder. Further evaluation confirmed the presence of IgG-κ-type MM. Chest CT revealed bilateral, diffuse GGOs predominantly in the middle and lower lung lobes, accompanied by thickened interlobular septa and multiple bone lesions, consistent with extramedullary disease. Flow cytometry analysis of bronchoalveolar lavage (BAL) fluid demonstrated CD19-negative, CD56-positive plasma cells with an abnormal cytoplasmic κ/λ light chain ratio, confirming clonal plasma cell infiltration and pulmonary involvement in MM. Treatment and Outcomes. The patient received bortezomib, resulting in significant resolution of the pulmonary GGOs on follow-up chest CT. Conclusion. This case highlights a rare presentation of MM with diffuse pulmonary GGOs on chest CT, mimicking interstitial lung disease. Furthermore, it underscores the diagnostic utility of BAL flow cytometry for identifying clonal plasma cells with atypical extramedullary involvement.