A Young Female With Low Back Pain Caused by Stage IV Lung Cancer

Abstract Low back pain is one of the most common symptoms, having a broad range of etiologies in differential diagnosis, such as inflammatory and degenerative disorders, malignancy and infections. Herein we present an interesting patient who initially presented with sacroiliitis and was ultimately diagnosed with stage IV lung cancer. She was initially misdiagnosed as axial spondyloarthritis. We aim to emphasize red flags in the differential diagnosis of sacroiliitis. Hypercalcemia and progressive, unbearable low back pain were supportive factors for underlying malignancy in our case.