Non-Blanching Rash / Petechiae / Purpura

First actions / assessment

• Assess ABCDE first and assume a high-risk cause until proven otherwise. Clarify onset, progression, whether the rash is petechiae or larger purpura, associated fever, headache, neck stiffness, photophobia, limb pain, myalgia, vomiting, diarrhoea, cough, bleeding symptoms, drug exposure, recent infection, sick contacts, travel, anticoagulant use, trauma, vomiting/coughing episodes, and any history of thrombocytopenia or vasculitis. Examine the entire skin surface including palms, soles, oral mucosa, and conjunctivae because petechiae may be easier to detect there, especially on darker skin. Assess vitals, capillary refill, perfusion, mental state, meningism, focal neurology, joint swelling, abdominal pain, and hepatosplenomegaly where relevant. Initial investigations commonly include CBC with platelets, blood film if indicated, coagulation profile, CRP, U&E/creatinine, lactate, blood cultures if sepsis is suspected, and further tests guided by cause such as coagulation studies for DIC/TTP or urinalysis for HSP/IgA vasculitis nephritis. The glass test is not sufficient to exclude evolving serious illness, and a blanching rash can become non-blanching as illness progresses.