Purpuric Rashes - Diagnosis and Treatment

How is a purpuric rash diagnosed?

Because there are so many causes, diagnosing the reason why you have developed a rash takes a bit of detective work. The doctor will need to ask you questions about the rash and your general health (take a history), examine you and do some tests.

What questions will I be asked?

The sort of questions the doctor will ask you may include:

  • How long you've had the rash.
  • Whether it's changed over time.
  • Whether you bruise easily.
  • Whether you've been abroad recently.
  • Whether you've recently taken any medicines you've bought from a pharmacy.
  • If this is not your regular GP:
    • Whether you've had any illnesses in the past or have any long-term conditions.
    • What prescribed medicines you are taking.
    • Whether you have any allergies.
    • Questions about your lifestyle (drinking, smoking, etc).

What will the doctor be looking for?

Examination of your rash and general body systems may give a clue as to the cause. The doctor will be looking for:

  • The size of the spots, whether they run together, whether there are any blisters (and whether they are filled with clear fluid, blood or pus).
  • Tenderness of the spots (this can happen with diseases causing inflammation, such as rheumatoid arthritis).
  • Any spots inside your mouth.
  • The location of the spots - for example, spots close together in one area are often seen where there has been injury, whereas spots on both lower legs suggest s problem with the circulation in your veins, as in the picture below:
  • Swollen organs in your tummy, such as an unusually large liver or spleen.
  • Numbness, weakness or other unusual features on examining your nervous system.

Will I need any tests?

There are a huge number of tests which could be arranged, but hopefully by the time the doctor has taken your history and examined you they will have a reasonable idea as to which are the most important. Most tests can be done on blood samples and may include:

  • A full blood count to check your platelets, white cells and red cells.
  • Inflammatory markers (tests to check for inflammation).
  • Tests to check how well your liver is working.
  • Tests to check your blood clotting system.
  • Tests to check for unusual levels of protein in your blood.
  • Tests to check for proteins that attack the body's own cells (autoantibodies).

Other tests may be ordered depending on the suspected cause. For example, you may need a blood culture if your doctor thinks you have an infection, or a lumbar puncture if they think you have a nervous system disorder.

How is a purpuric rash treated?

The treatment will depend on the cause. Leaflets on the specific conditions mentioned in the Causes section will give you more details. If your platelet count is very low, the first treatment you will receive will be a platelet transfusion.

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  • Purpura; University of Maryland Medical Centre
  • Maher GM; Immune thrombocytopenia. S D Med. 2014 Oct 67(10):415-7.
  • Purpura; Internal Medicine Reference
Dr Laurence Knott
Peer Reviewer:
Prof Cathy Jackson
Document ID:
29413 (v1)
Last Checked:
08 July 2017
Next Review:
07 July 2020

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.