·Viral infections, most commonly enteroviral.
·Septicaemia, most commonly meningococcal.
·Thrombocytopenia, platelet, or clotting disorders.
·Vasculitis, e.g. HSP.
·Trauma, including NAI.
·Vasomotor straining, e.g. strenuous coughing or isometric exercise.
If the patient is well and there is an obvious benign cause, reassure as the rash will resolve spontaneously. If cause unclear, initial investigations should include:
·Check BP, urinalysis, blood U&E and ASOT (if HSP likely).
·If sepsis possible, admit and start IV antibiotics.
·Stop any drug likely to be causative.
·Consider a skin biopsy if diagnosis remains unclear.