Probable diagnosis is Henoch-Schonlein purpura . Henoch-Schonlein purpura is a small-vessel vasculitis caused by immune complex deposition following an infectious trigger. It is predominantly a disease of children and young adults. The usual presentation is with purpura over the buttocks and lower legs, accompanied by abdominal pain, gastrointestinal bleeding and ahralgia. Nephritis can also occur and may present up to 4 weeks after the onset of other symptoms. Biopsy of affected tissue shows a vasculitis with IgA deposits in the vessel wall. Henoch-Schonlein purpura is usually a self-limiting disorder that settles spontaneously without specific treatment. Glucocoicoids and immunosuppressive therapy may be required in patients with more severe disease, paicularly in the presence of nephritis. Ref - davidsons 23e p1043