Paraneoplastic Sacroiliitis: A Masquerade of Inflammatory Arthritis in Leukemia.

Leukemic arthritis is a rare but clinically significant presentation of leukemia, often resembling inflammatory or autoimmune arthritis. Axial joint involvement, particularly sacroiliitis, is an uncommon manifestation and can mislead clinicians, delaying the diagnosis of the underlying hematologic malignancy. We present the case of a 34-year-old woman with persistent low back pain, initially diagnosed as sacroiliitis and treated with conventional therapies. Despite partial symptom relief with nonsteroidal anti-inflammatory drugs and corticosteroids, her condition worsened, leading to further evaluation. Subsequent laboratory tests revealed leukocytosis and anemia, and a peripheral blood smear confirmed leukemic infiltration. The final diagnosis of paraneoplastic sacroiliitis secondary to acute leukemia was established. This case highlights the importance of considering malignancy in patients presenting with refractory arthritis, particularly when symptoms are atypical or fail to respond to standard treatments. Early recognition and prompt initiation of chemotherapy can significantly improve clinical outcomes.​.