<prompt> In Henoch schonlen purpura Ig and complement involved:IgG, C 3IgA, C 3IgA, ClIgG, Cl  <response>: Ans. b IgA, C 3Ref: Harrison 19th ed. 2190 Henoch Schonlein purpura is a small-vessel vasculitis in which complexes of immunoglobulin A IgA and C3 are deposited on arterioles, capillaries, and venules. As with IgA nephropathy, serum levels of IgA are high in HSP . IgA nephropathy has a predilection for young adults while HSP is more predominant among children. Further, IgA nephropathy typically only affects the kidneys while HSP is a systemic disease. HSP involves the skin and connective tissues, scrotum, joints, gastrointestinal tract and kidneys. Investigation: IgA levels high, platelet count normal and skin biopsy IOC. Treatment: steroids 