Hypocomplementemic Urticarial Vasculitis (Anti-C1q Vasculitis)

Hypocomplementemic Urticarial Vasculitis (Anti-C1q Vasculitis) is a rare autoimmune condition that primarily affects the skin and sometimes other organs. It causes recurrent hives that last longer than typical allergic reactions and are often painful or burn rather than itch. The disease involves inflammation of small blood vessels, leading to damage and symptoms like joint pain, eye inflammation, and sometimes kidney problems. This condition is linked to low levels of certain proteins in the blood called complement, which normally help fight infections and clear damaged cells. The immune system mistakenly attacks these proteins, causing ongoing inflammation and symptoms.

Hypocomplementemic Urticarial Vasculitis (Anti-C1q Vasculitis) is a systemic small vessel vasculitis characterized by immune complex deposition and activation of the classical complement pathway, leading to hypocomplementemia. It is caused by autoantibodies against the C1q component of complement, resulting in persistent urticarial skin lesions that histologically show leukocytoclastic vasculitis. The disease often involves multiple organ systems including the skin, joints, eyes, and kidneys, with clinical features such as urticarial rash, arthralgia, glomerulonephritis, and ocular inflammation. The hallmark is low serum levels of C1q, C3, and C4 due to complement consumption. It is important to distinguish this condition from other urticarial and vasculitic disorders because of its systemic involvement and potential for significant morbidity.