Purpura and Petechiae

Differential Diagnosis

Common Diagnoses

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

TraumaSenile PurpuraLiver DiseaseIncreased IV PressureDrugs
Tender BruisingYesNoNoNoNo

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.

Published: 2nd August 2022 Updated: 10th April 2024

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