Purpura and Petechiae
Purpura are reddish-purple lesions which do not blanch with pressure. When less than 1 cm in diameter, they are called petechiae; if larger, they are known as ecchymoses. The problem often presents as ‘bruising easily’ and is a common ‘while I’m here’ complaint in primary care. Most cases are normal, with causative minor trauma simply being forgotten or unnoticed.
Differential diagnosis
Common Diagnoses
- Trauma
- Senile Purpura
- Liver Disease (Especially Alcoholic Cirrhosis)
- Increased Intravascular Pressure, e.g. Coughing, Vomiting, Gravitational
- Drugs, e.g. Steroids, Warfarin, Aspirin
Occasional Diagnoses
- Vasculitis (e.g. Henoch–Schönlein Purpura, Connective Tissue Disorders)
- Thrombocytopenia (e.g. Idiopathic Thrombocytopenia Purpura [ITP]), Bone Marrow Damage (e.g. Lymphoma, Leukaemia, Cytotoxics), Aplastic Anaemia
- Renal Failure
- Infective Endocarditis
Rare Diagnoses
- Paraproteinaemias (e.g. Cryoglobulinaemia)
- Inherited Clotting Disorders (e.g. Haemophilia, Christmas Disease, Von Willebrand’s Disease)
- Infections (e.g. Meningococcal Septicaemia, Rocky Mountain Spotted Fever)
- Vitamin C and K Deficiency
- Disseminated Intravascular Coagulation (DIC)
- Congenital Vessel Wall Abnormalities (e.g. Ehlers–Danlos Syndrome)
Ready reckoner
Key distinguishing features of the most common diagnoses
| Trauma | Senile Purpura | Liver Disease | Increased IV Pressure | Drugs | |
|---|---|---|---|---|---|
| Tender Bruising | Yes | No | No | No | No |
| Spontaneous | No | Possible | Yes | No | Yes |
| Widespread | No | Yes | Yes | No | Yes |
| Recurrent | No | Yes | Yes | No | Possible |
| Petechial | Possible | No | No | Yes | Possible |
Possible investigations
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
Top Tips
- 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.
Red Flags
- 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.