Paraneoplastic Arthritis in a Patient With Gastric Cancer: A Case Report.

Paraneoplastic syndromes occur in the presence of a tumor and are known to cause a myriad of systemic manifestations by mechanisms other than direct metastasis. Although considered to be rare, tumors can cause paraneoplastic rheumatological manifestations such as paraneoplastic arthritis. Differentiating between paraneoplastic arthritis and primary rheumatoid arthritis (RA) presents a diagnostic challenge to physicians. Here we describe a case of an 83-year-old male with complaints of painful joint swelling of his hands, elbows, and feet. Subsequent tests ultimately led to the diagnosis of gastric cancer with associated paraneoplastic arthritis. We highlight the physical, laboratory, and imaging findings associated with the diagnosis of paraneoplastic arthritis with emphasis on the differences between this diagnosis and that of RA. Despite the uncommon nature of paraneoplastic arthritis, it remains of paramount importance to be aware of its association with malignancies, aiding in possible earlier diagnosis.