<prompt> Hypersensitivity angiitis is seen in -SLEPolyarteritis nodosaHenoch schonlein purpuraBuergers disease  <response>: HSP is not hypersensitivity angiitis. But the best answer amongst the given options is HSP because it is the most important differential of hypersensitivity angiitis.Hypersensitivity angiitis Hypersensitivity vasculitis or hypersensitivity angiitis or leukocytoclastic angiitis is a small vessel vasculitis due to hypersensitivity reaction.It is usually to a known drug, e.g. cefoperazone, autoantigens or infectious agents.Immune complexes lodge in the vessel wall, attracting polymorphonuclear leukocytes who in turn release tissue-degrading substances leading to an inflammatory process.Hypersensitivity angiitis usually presents with skin manifestation, e.g. palpable purpura, but sometimes nerves, kidneys, joints and heart may also be involved.Diagnostic criteriaAt least 3 out of the 5 criteria are requiredAge 16Use of possible triggering drug in relation to symptoms.Palpable purpuraMaculopapular rashSkin biopsy showing neutrophil infiltrate around the vessel.Henoch-schonlein purpura is the most important differential. 