[Hypocomplementemic urticarial vasculitis]

Hypocomplementemic urticarial vasculitis (HUV), called anti-C1q vasculitis in the 2012 revised International Chapel Hill Consensus Conference Nomenclature of Vasculitides, is a rare systemic vasculitis of unknown etiology, affecting small vessels. HUV is characterized by urticarial lesions, hypocomplementemia and systemic manifestations, mostly musculoskeletal and ocular, but also gastrointestinal, pulmonary and kidney involvement. Anti-C1q antibodies are detected in only half of the patients, and low C1q seems to represent a more sensitive marker. Published data on the therapeutic management are scarce in the literature. Hydroxychloroquine and colchicine seem to represent effective first-line therapies. In patient with relapsing or refractory disease, response rates appeared slightly higher for corticosteroids together with conventional immunosuppressive agents, in particular azathioprine, mycophenolate mofetil, or cyclophosphamide, while a rituximab-based regimen tended to have higher efficacy. The best strategy for treating HUV has yet to be defined.