Abstract
Acute polyarthritis requires a comprehensive differential diagnosis in order to establish its etiology. Moreover, sometimes it may unfold unexpected comorbidities, thus necessitating an individualized management approach.
This article describes the case of an elderly patient whose initial presentation of acute polyarthritis was interpreted as crystal induced-arthritis demonstrated by the presence of calcium pyrophosphate and lipid crystals in the synovial fluid. The clinical deterioration of the patient along with the suspicion of a systemic infection required interdisciplinary collaboration and led to his transfer to the infectious diseases department where the diagnosis of sepsis from unknown origin was added. Further investigations unmasked a large complicated pancreatic pseudocyst that eventually ruptured into the peritoneal cavity and led to the patient's death.