Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease where the immune system mistakenly attacks its own healthy tissues and organs, including the skin, joints, kidneys, and brain. Vasculitis, the inflammation of blood vessel walls, is a recognized and potentially serious complication of SLE. This inflammation can narrow, weaken, or block vessels, restricting blood flow to the tissues they supply. Lupus frequently causes vasculitis, known as lupus vasculitis, which occurs in approximately half of all SLE patients.
Defining the Autoimmune Link Between Lupus and Vasculitis
The underlying cause of lupus vasculitis is linked to the core mechanisms of SLE activity. Lupus produces autoantibodies, specialized proteins that target the body’s own components, such as nuclear material. These autoantibodies bind to their targets, forming circulating immune complexes (IC).
These immune complexes become trapped within blood vessel walls, initiating an inflammatory response. The deposition of these complexes activates the classical complement cascade, a powerful part of the immune system. Activation of complement components and the recruitment of white blood cells trigger a heightened inflammatory state within the vessel wall.
This infiltration of inflammatory cells damages the endothelium, the inner lining of the blood vessel. The resulting inflammation causes the vessel wall to swell and thicken, impeding blood flow to surrounding tissues. This process is classified as a secondary vasculitis arising from the pre-existing autoimmune condition, SLE.
Spectrum of Vessel Involvement and Classification
Lupus vasculitis is classified based on the anatomical size of the blood vessels affected, ranging from the smallest capillaries to the largest arteries. The most common presentation is small-vessel vasculitis, which primarily affects tiny post-capillary venules and capillaries. This form is often localized to the skin, known as cutaneous vasculitis.
Small-vessel involvement typically results in milder, often recurrent, symptoms. Medium-sized vessels, such as arterioles and smaller veins, can also be affected, leading to more widespread and serious systemic issues. Involvement of the largest vessels, such as the aorta and its major branches, is exceedingly rare.
The size of the vessel dictates the pattern of disease. Small-vessel inflammation causes pinpoint bleeding and rashes, while inflammation in medium vessels can significantly reduce blood supply to major organs. Inflammation outside of the skin classifies the condition as systemic vasculitis, which carries a more serious prognosis and can range from a single organ to a life-threatening, multi-organ disease.
Clinical Presentation and Organ Manifestations
The symptoms of lupus vasculitis are highly varied and depend on which organ system’s blood supply is compromised. Skin manifestations are the most frequent presentation, often appearing as palpable purpura—raised, non-blanching red or purple spots, typically on the lower legs. Other common findings include petechiae, urticaria-like lesions, livedo reticularis, and small ulcers resulting from localized tissue death.
When vasculitis affects the nervous system, it impacts both the central and peripheral nerves. Central nervous system involvement may cause severe headaches, cognitive dysfunction, or seizures due to restricted blood flow. In the peripheral nerves, inflammation can lead to mononeuritis multiplex, involving damage to two or more isolated nerve areas, often presenting as weakness, numbness, or tingling.
Vasculitis can severely affect the gastrointestinal tract, known as lupus mesenteric vasculitis (LMV). Inflammation of the intestinal blood vessels causes acute abdominal pain, nausea, vomiting, and can lead to bowel ischemia or perforation, which is a medical emergency. This visceral involvement highlights the potential for systemic vasculitis to be life-threatening.
Renal involvement is complex, often overlapping with lupus nephritis. While lupus nephritis is driven by immune complex deposition in the kidney’s filtering units, true renal vasculitis involves inflammation and fibrinoid necrosis of the kidney’s microvessels. This specific microvascular lesion is associated with a rapidly progressive decline in kidney function, requiring prompt recognition and treatment.
Diagnosis and Management Strategies
Diagnosing lupus vasculitis requires integrating clinical findings with laboratory and imaging results. Initial laboratory tests look for general signs of systemic inflammation, such as elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Autoantibody screening, particularly for anti-dsDNA and complement levels (C3 and C4), helps assess overall SLE disease activity, which often correlates with vasculitis.
While blood tests suggest inflammation, a tissue biopsy is often necessary for a definitive diagnosis. A skin biopsy from a purpuric lesion can microscopically confirm inflammation and immune complex deposition in the vessel walls. For larger vessel involvement, imaging techniques like computed tomography (CT) angiography or magnetic resonance angiography (MRA) visualize vessel narrowing or blockages.
Management focuses on rapidly suppressing the immune system to reduce inflammation and prevent irreversible organ damage. The initial approach involves high-dose corticosteroids, such as prednisone, to quickly control the inflammatory flare. Once the acute phase is managed, treatment is escalated to include more potent immunosuppressive agents.
These immunosuppressive medications, such as cyclophosphamide, azathioprine, or mycophenolate mofetil, work to quiet the underlying autoimmune response of SLE. Biologic therapies, including rituximab, may also be employed in more severe or refractory cases to specifically target the immune cells driving the disease. The treatment plan is always tailored to the severity of the vasculitis and the specific organs that are involved.