Why can systemic lupus erythematosus cause fever and weight loss?

In systemic lupus erythematosus (SLE), fever and weight loss are classified as constitutional symptoms, which are often the initial manifestations of the illness.1

These symptoms arise because SLE is a chronic inflammatory disease characterized by a breakdown of the immune system. The body produces autoantibodies that react with components of its own tissues, forming immune complexes that deposit in various organs and structures. This widespread autoimmune reaction triggers persistent, systemic inflammation throughout the body.213

Fever is a common physiological response to this ongoing inflammatory process, while weight loss and general fatigability often result from the body’s systemic struggle against its own tissues. Because the disease can affect virtually any organ system—including the gastrointestinal tract, joints, and serous membranes—the resulting inflammatory burden frequently manifests as these non-specific constitutional symptoms before more localized organ damage becomes apparent.12