Henoch schonlein purpura, also known as HSP or IgA vasculitis, is the most common small vessel vasculitis in children. Cases are commonly preceded by upper respiratory infections, and the disease is caused by deposition of immune complexes consisting of IgA antibodies bound to an circulating antigen. In other words, HSP is a type 3 hypersensitivity reaction, and the deposition of IgA immune complexes in various sites leads to the symptoms of the disease. Immune complex deposition in the small vessels of the skin leads to palpable purpura over the buttocks and legs, while IgA deposition in the small vessels of the GI system can lead to abdominal pain that may be complicated by intussusception. Immune complex deposition in joints leads to non-specific arthralgias, and deposition in the kidney leads to glomerulonephritis. In particular, IgA-mediated vasculitis in the kidney is also known as IgA nephropathy or Berger’s disease.