Case Presentation: A 73 year old female with previous history of IgG lambda multiple myeloma presented to the emergency room with three weeks of gradually worsening shortness of breath, fatigue, and loss of appetite. Her multiple myeloma was diagnosed 2.5 years ago and she had since undergone several rounds of radiation and chemotherapy. Upon arrival to the emergency department, she was noted to be saturating 85% on room air requiring 3 liters supplemental oxygen via nasal cannula. Chest x-ray showed a large left-sided pleural effusion for which a thoracentesis and chest tube placement were performed draining 450 mL of bloody-brown fluid. Fluid analysis indicating exudative fluid with cytology showing lambda-restricted plasma cell neoplasm suggestive of a myelomatous pleural effusion (MPE). Computed Tomography Angiography (CTA) was negative for pulmonary embolism. After her diagnosis, Hematology-Oncology was consulted for treatment options given her poor prognosis. The patient opted for continued chemotherapy treatment as opposed to hospice given she wanted to attend her grandson’s wedding in a couple months. Later, her chest tube’s output decreased and was removed at discharge. In addition, she had improvement in her shortness of breath and no longer required supplemental oxygen. Given the high likelihood of pleural fluid reaccumulation, the patient was discharged with close outpatient follow-up with pulmonology for evaluation of PleurX catheter placement.

Discussion: Pleural effusions occur in 6% of patients with multiple myeloma. The etiology can be multifactorial with causes such as congestive heart failure, renal failure, nephrotic syndrome, parapneumonic effusions or amyloidosis. Our patient demonstrates a rare case of a myelomatous pleural effusion, an exudative effusion, which is a direct result of multiple myeloma and occurs in < 1% of cases. Unfortunately, it carries a very poor prognosis. Pleural cytology has diagnosis rate for malignancy of around 60% with detection of atypical plasma cells in pleural fluid. If inconclusive, detection of monoclonal protein with pleural fluid electrophoresis or histological confirmation with pleural biopsy may be required. Patient have an median life expectancy of 4 months once diagnosed given resistance to aggressive chemotherapy treatment. Recurrent pleural effusions may require palliative pleurodesis as treatment.

Conclusions: Myelomatous pleural effusions (MPE) are rare, but carries a very poor prognosis with an aggressive natural course. This case demonstrates that physicians should not become complacent when investigating pleural effusions outside of primary cardiac, pulmonary, and renal etiologies. Patients with exudative pleural effusions in the setting of multiple myeloma require cytological fluid studies to aid in rapid diagnosis and initiation of treatment, whether palliative approach or aggressive chemotherapy.