Vasculitis denotes affection of small to medium sized vessels by polyangitis. Antineutrophil cytoplasmic antibodies (ANCA) are immunoglobulin G (IgG) autoantibodies directed against constituents of neutrophil granules leading to neutrophil degeneration which results in cell apoptosis known as "Natoptosis" (NaTosis) of the cells. These lead to vessel endothelial cell damage. So that, ANCA formation seems to be the basic reaction in vasculitis. Complement activation at C3 and C4 was thought to be involved in renal damage ANCA associated vasculitis (AAV).
Inclusion Criteria: * Infants \& children with vasculitis attending Assiut University Child Hospital (AUCH), aged \> 1 mo. - 17yr. of both genders will be included during 2 years of study. Exclusion Criteria: * Those cases aged less than one month will be excluded from the study.