Urticarial Vasculitis (UV) is a rare inflammatory disorder that targets the small blood vessels of the skin. The name is derived from “urticaria” (hives) and “vasculitis” (inflammation of the blood vessels). This condition is characterized by chronic or recurrent episodes of persistent, hive-like skin lesions, which are caused by underlying inflammation of the vessel walls. UV is generally considered an immune-mediated disorder where the body mistakenly attacks the lining of these small vessels.
What Urticarial Vasculitis Is
UV is a form of cutaneous small-vessel vasculitis. The underlying mechanism involves an immune response, often classified as a Type III hypersensitivity reaction, where immune complexes deposit in the vessel walls. These deposits activate the complement system, triggering an inflammatory cascade involving immune cells like neutrophils.
This process causes damage to the vessel walls, known as leukocytoclastic vasculitis on a skin biopsy. This vessel damage differentiates UV from common urticaria, or ordinary hives. While the underlying cause is often unknown (idiopathic), the condition can be triggered by infections, certain medications, or associated with other autoimmune disorders.
Clinical Signs and Presentation
The skin lesions are typically raised wheals or plaques that look similar to common hives but possess distinct features. Unlike standard urticaria, which resolves within 2 to 8 hours, UV lesions persist in the same location for longer than 24 hours, often lasting several days. These persistent lesions are frequently accompanied by a burning or painful sensation rather than the intense itchiness associated with typical hives.
The individual plaques may appear red-rimmed with a paler center and are often indurated, feeling firm or hardened to the touch. As the lesions resolve, they commonly leave behind residual skin changes. This often appears as a bruise-like discoloration, known as post-inflammatory hyperpigmentation or purpura, which is a key sign not seen in chronic spontaneous urticaria.
Classifying the Condition
Urticarial Vasculitis is classified into two main types based on the level of complement proteins found in the blood. Testing these levels helps determine the potential severity and risk of systemic involvement beyond the skin.
Normocomplementemic Urticarial Vasculitis (NUV)
NUV is the more common type, characterized by normal levels of complement proteins. This form is generally limited to the skin, and patients typically have a better prognosis with fewer complications affecting internal organs. Management often focuses primarily on controlling the cutaneous symptoms.
Hypocomplementemic Urticarial Vasculitis (HUV)
HUV is the less common and often more severe variant, identified by abnormally low levels of complement proteins, specifically C3 and C4. This reduction suggests active consumption by the immune system, which increases the likelihood of systemic disease. HUV is frequently associated with systemic symptoms, including joint pain (arthralgia), fever, and inflammation affecting the eyes, lungs, or kidneys. HUV also has a strong association with underlying autoimmune disorders, most notably Systemic Lupus Erythematosus (SLE). Patients with HUV often have specific autoantibodies, such as anti-C1q antibodies, which contribute to chronic inflammation and systemic risk.
Treatment and Management
Management is tailored to the severity of the disease and whether internal organs are involved. For mild cases limited to the skin, treatment begins with symptomatic relief medications, including H1 and H2 antihistamines for itching, and nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce general inflammation.
If the skin disease is persistent or more severe, first-line anti-inflammatory agents are employed, such as dapsone, colchicine, or hydroxychloroquine. These medications suppress the underlying inflammation with a lower risk profile than high-dose steroids.
For patients with significant systemic involvement (especially HUV) or disease unresponsive to initial treatments, more potent immunosuppressive therapy is necessary. This often involves oral corticosteroids, sometimes combined with other immune-suppressing drugs. Agents like azathioprine, methotrexate, or mycophenolate mofetil may be used to achieve long-term control and minimize the side effects associated with prolonged corticosteroid use.