A Rare Case of Malignant Mesothelioma Presenting with Systemic Lupus Erythematosus Seropositivity: A Case Report and Review of Literature.

While malignant mesothelioma may initially present in a variety of ways, it is uncommon to present with systemic lupus erythematosus (SLE) seropositivity and thus obscuring its diagnosis. Our case involves a 75-year-old Caucasian male with a past medical history of essential hypertension, remote prostate cancer status post prostatectomy, and lifetime nontobacco use presenting with progressive shortness of breath over one month. After a negative cardiac assessment, a postcardiac catheterization chest X-ray (CXR) revealed a right-sided moderate-to-large pleural effusion that, on further workup, was found to be exudative. Effusion studies were negative for malignancy and bacterial growth. Recurrent accumulation of fluid after a thoracentesis one week prior prompted an autoimmune work up. Positive markers included antinuclear antibodies, anti-double stranded DNA antibodies, and anti-histone antibodies, while anti-Smith antibodies were negative. Although SLE was initially suspected based on serologies, no clinical signs or symptoms were present to fulfill the diagnosis criteria. A trial of oral prednisone resulted in decreased pleural effusion size with no further recurrence. Additional studies included a CT scan of the chest that showed pleural masses confirmed with biopsy to be epithelioid mesothelioma. Given the patient's age and new diagnosis of malignant mesothelioma, we hypothesized that the presence of autoantibodies was likely false positives due to acquired autoantibodies with age, hyperactivity of the immune system from malignancy, and possible prior asbestos exposure.