Ig and complement deposition in and around the vessel wall is one of the symptoms of urticarial vasculitis urticarial vasculitis was first reported by MCDuffie in 1973 and is characterized by a rash that is windy and long-lasting with hypocomplementemia. Inflammatory mediators damage vascular endothelial cells and therefore vasculitic changes occur, showing signs of leukocytoclastic vasculitis. What are the tests for urticarial vasculitis? 1.Laboratory examination It can be seen that blood sedimentation is increased, serum complement level is decreased, autoantibody titer is positive (ANA, dsDNA antibody, anti-SSA/SSB antibody), rheumatoid factor is positive, and circulating immune complex level is increased. 2. Ancillary examination methods (1) Routine blood tests: normal or increased peripheral blood leukocyte count, increased neutrophil ratio, and rapid hematocrit may be found. The most common is severe and persistent hypocomplementemia, especially C4 reduction is more obvious. (2) Direct fluoroscopy: shows immunoglobulin and complement granular deposits in and around the vessel wall. (3) Radiological examination: frontal and lateral x-ray of the chest and lymphography of both lower extremities. (4) Pathological examination: lymph nodes, skin biopsy and liver puncture biopsy if necessary. The disease is most often seen in middle-aged women, with the age of onset mostly between 30 and 40 years. The onset of the disease is often accompanied by irregular fever, sometimes up to 38-39°C. 2. The main characteristic of the skin is a wind cluster, which is very similar to urticaria. However, the lesions last for a long time, often 24 to 72 hours, or even several days, and do not disappear; itching or burning sensation; infiltration when touched, sometimes punctate bleeding can be seen in the lesions; a few cases have blisters, but no necrosis; pigmentation or desquamation remains after the damage subsides. The disease is often associated with arthralgia and arthritis, mainly in the joints of the extremities, sometimes with joint swelling. There may also be abdominal discomfort and enlarged lymph nodes. Renal damage may occur in the late stages. In a few cases, epilepsy, meningitis and unilateral optic neuritis may occur. Vasculitic urticaria is often an early symptom of dermatomyositis, allergic vasculitis, SLE, etc. Therefore, changes in the course of the disease should be closely observed.