Urticarial Vasculitis (UV) is a rare inflammatory condition that affects the small blood vessels, presenting on the skin with lesions that closely resemble common hives, or urticaria. Classified as a form of small-vessel vasculitis, the body’s immune system mistakenly targets and inflames the walls of these tiny vessels. This inflammation and damage sets UV apart from typical allergic hives, which are caused by histamine release in the skin. Because the inflammation occurs directly in the blood vessels, UV is a more serious diagnosis than standard urticaria and requires specific medical investigation.
The Defining Characteristics of Urticarial Vasculitis
The skin lesions associated with Urticarial Vasculitis appear as raised, red patches or wheals, but they possess specific characteristics that differentiate them from ordinary hives. The most telling clinical sign is the duration of the individual lesions, which remain in a fixed spot for longer than 24 hours before they begin to resolve. In contrast, a typical hive outbreak consists of lesions that usually fade and reappear elsewhere within a few hours.
Patients often report that the lesions cause a painful or burning sensation, which is less common with allergic hives that are usually intensely itchy. As these lesions heal, they frequently leave behind a visible mark, such as a bruise-like discoloration or post-inflammatory hyperpigmentation, a consequence of the damaged blood vessels leaking blood into the surrounding tissue. This process of inflammation and destruction within the vessel wall is known histologically as leukocytoclastic vasculitis.
Beyond the skin, Urticarial Vasculitis can present with systemic symptoms, indicating involvement of other organ systems. These manifestations may include joint pain (arthralgia), recurrent fever, and general malaise. In more severe presentations, patients may experience abdominal pain, angioedema, or issues affecting the lungs and kidneys.
Underlying Causes and Associated Conditions
While the precise cause of Urticarial Vasculitis is often unknown (idiopathic), it is frequently triggered by or associated with an underlying disease or exposure. The condition is widely considered an autoimmune disorder where the immune system generates complexes that deposit in the vessel walls, leading to inflammation. Many cases are linked to systemic autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) or Sjögren’s Syndrome.
Infections can also serve as a trigger, including viruses like Hepatitis B and Hepatitis C, as well as infectious mononucleosis. Certain medications, including some antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs), have been reported to induce an episode of UV. The condition is broadly classified into two types based on levels of complement proteins: Normocomplementemic and Hypocomplementemic UV.
Normocomplementemic UV involves normal complement levels and is generally associated with disease limited to the skin, carrying a better outlook. Hypocomplementemic UV shows low levels of complement proteins (C3 and C4) and is strongly linked to more severe systemic involvement, including a higher risk of associated connective tissue diseases like SLE.
Diagnostic Testing and Confirmation
A definitive diagnosis of Urticarial Vasculitis requires more than just a physical examination, as the skin rash can mimic common hives. The most important test is a skin biopsy taken from a fresh lesion, ideally one present for less than 48 hours. This tissue sample is examined under a microscope for the characteristic signs of leukocytoclastic vasculitis, confirming inflammation and destruction of the small blood vessel walls.
Blood work is essential for classifying the disease and identifying any associated conditions. Testing for complement components (C3 and C4) determines if the patient has the Normocomplementemic or Hypocomplementemic form of UV. Low complement levels are a warning sign of potential multi-organ disease and require more intensive investigation.
Further laboratory tests include screening for autoantibodies, such as the Antinuclear Antibody (ANA), which helps determine if an underlying autoimmune disorder like lupus is present. Screening for viral infections like Hepatitis B and C is also standard practice, as treating the underlying infection can sometimes resolve the vasculitis.
Treatment and Long-Term Management
The approach to treating Urticarial Vasculitis is tiered and depends heavily on the severity of the symptoms and whether systemic organs are involved. For milder cases where the disease is limited to the skin, first-line treatments are aimed at controlling inflammation and managing symptoms. Non-steroidal anti-inflammatory drugs (NSAIDs) or H1-antihistamines may be used to provide relief from the burning or painful sensations.
When the disease is more extensive, or if systemic symptoms like joint pain or kidney involvement are present, more potent anti-inflammatory or immunosuppressive agents are necessary. Oral corticosteroids, such as prednisone, are often introduced to rapidly suppress inflammation. For long-term control and to reduce reliance on corticosteroids, other medications like dapsone, hydroxychloroquine, or colchicine may be used.
In cases of severe, organ-threatening, or treatment-resistant disease, powerful immunosuppressants become the standard of care. These include medications such as azathioprine, methotrexate, or mycophenolate mofetil, which modulate the overactive immune response. Treatment is tailored not only to symptom control but also to addressing any underlying cause, such as managing associated autoimmune diseases.