What is the main clinical sign of Systemic Lupus Erythematosus (SLE)?

The main clinical sign of Systemic Lupus Erythematosus (SLE) is non-erosive polyarthritis. This sign is often one of the first presentations of the disease and is notable because it involves pain, swelling, and stiffness in multiple joints without joint destruction or erosion, which differentiates it from other forms of arthritis.

In SLE, the polyarthritis can vary in severity among patients and may affect both small and large joints, contributing to significant morbidity. It is an immune-mediated condition where hyperactive immune responses lead to inflammation in various tissues, and the joints are commonly affected without the permanent damage seen in certain other arthritic conditions.

Other clinical signs such as skin rashes, renal dysfunction, and photosensitivity may also occur in SLE and can be quite prominent in patients. However, the non-erosive polyarthritis often serves as a hallmark of the disease, particularly in the early stages, and is crucial for diagnosis along with other symptoms and laboratory findings.