Petechiae are small purpuric lesions up to 2mm in diameter that are usually flat and don’t blanch when pressure is applied.
Like purpura petechiae are due to haemorrhage from small blood vessels. Differentials are wide and include:
- Platelet disorders including thrombocytopenia (low platelets) or poor platelet function due to causes such as idiopathic thrombocytopenic purpura (ITP), bone marrow disorders (such as aplastic anaemia, leukaemia)
- Other coagulation disorders such disorders of the clotting cascade, disseminated intravascular coagulation (DIC)
- Infection, including many causative organisms such as influenza, group A streptococcus, Neisseria meningitides
- Vascular disorders due to leaky blood vessels