Key distinguishing features of the most common diagnoses
|Trauma||Senile Purpura||Liver Disease||Increased IV Pressure||Drugs|
Likely:FBC, ESR/CRP, INR (if on warfarin).
Possible:LFT, U&E, coagulation screen, plasma electrophoresis.
Small Print:Autoimmune testing, further hospital investigations (see below).
- FBC, ESR/CRP: FBC may reveal thrombocytopenia or evidence of blood dyscrasia. ESR/ CRP and WCC may be raised in blood dyscrasia, connective tissue disorder and infection.
- LFT, U&E: For underlying liver or renal disease.
- INR: If on warfarin
- Autoimmune testing: If possible connective tissue disease causing vasculitis
- Coagulation screen: To test haemostatic function (e.g. bleeding time, prothrombin time, activated partial thromboplastin time).
- Plasma electrophoresis: For hypergammaglobulinaemia, paraproteinaemia and cryoglobulinaemia.
- Further investigations (usually secondary care): To investigate underlying cause, e.g. skin biopsy to confirm vasculitis, bone marrow biopsy if possible marrow infiltrate
- Multiple bruises of varying ages on the legs of young children who are otherwise well and have no other stigmata of clotting disorder or abuse are likely to be non-pathological.
- Senile purpura should be easy to diagnose from the history and examination. Reassurance, rather than investigation, is required.
- A few petechiae on or around the eyelids of a well child can be caused by vigorous coughing or vomiting. If the history is clear, explain the cause to the parents – but emphasise that the appearance of an identical rash elsewhere requires urgent attention.
- The distribution of purpura can give useful clues to the diagnosis. On the legs, platelet disorders, paraproteinaemias, Henoch–Schönlein purpura or meningococcal septicaemia are likely; lesions on the fingers and toes indicate vasculitis; and senile and steroid purpura tend to affect the back of the hands and arms.
- Purpura caused by vasculitis tend to be raised palpably above the skin.
- Remember that the rash of meningococcal septicaemia can appear before a child is obviously systemically unwell. If there is any suspicion that this might be the diagnosis, give parenteral penicillin and admit immediately.
- The absence of a family history does not exclude a significant inherited bleeding disorder – these disorders can arise spontaneously
- Take very seriously the pale patient with purpura – a bone marrow problem is likely. Arrange an urgent FBC or admit.
- Always do a full surface examination of a child with bruising, not forgetting the anogenital area. Keep non-accidental injury in mind.
- Never give an IM injection if a serious bleeding disorder is suspected.