Purpuric Rashes

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Purpura is a purplish discoloration of the skin produced by small bleeding vessels near the surface. Purpura may also occur in the mucous membranes, especially of the mouth, and in the internal organs. Purpura is not a disease per se but is indicative of an underlying cause of bleeding.

When purpura spots are very small (<1 cm in diameter), they are called petechiae or petechial haemorrhages. Larger, deeper purpura are referred to as ecchymoses or bruising.

Purpura may occur with either normal platelet counts (non-thrombocytopenic purpuras) or decreased platelet counts (thrombocytopenic purpuras). Platelets help maintain the integrity of the capillary lining as well as being important in the clotting process. As a general rule, purpura indicates a problem of the platelet system whilst a deficiency of clotting factors will cause haematomas or haemarthrosis as in haemophilia. Nevertheless, clotting factor deficiency must be considered.

The appearance of purpura is quite characteristic and it does not blanch on pressure.



It may seem unusual to place examination before history but there is some logic to this. In reality, the patient is likely to start the consultation by presenting the rash and so inspection of the rash and noting such matters as the general condition of the patient will occur at the outset:

  • Note the nature of the lesions - size, confluence, associated blisters (and what these contain: exudate, blood, pus).
  • Where are the lesions? For example, localised lesions may be caused by trauma whereas purpura due to venous hypertension will be in the lower legs with a distribution as shown below.
  • Don't forget to ask/look for lesions in the mucous membranes.
  • Tenderness may suggest an inflammatory process.

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  • Note the age of the patient. Henoch-Schönlein purpura tends to occur in children.[4] Senile purpura is confined to the elderly.[5] Leukaemia and myeloproliferative disorders can occur at any age.
  • How long has the rash been present? Is it changing noticeably? Meningococcal septicaemia will be very recent in origin and changing almost visibly.
  • Is the patient otherwise well? If a child has developed a purpuric, possibly meningococcal, rash but does not seem unwell, do not be lured into a false sense of security. That child may be moribund just 20 minutes later.
  • Has general easy bruising been noticed?

Other components of a routine history should be gone through (past medical history, medical and allergic history - including any over-the-counter drugs - and social history are all relevant).


Having inspected the skin and taken a history, it may be useful to return to a physical examination to reassess the rash and carry out a further systemic examination, looking for hepatomegaly/splenomegaly or neurological signs for example. Be guided by your findings so far.

Purpura is a sign rather than a diagnosis and a cause must be sought. It is helpful to classify causes into vascular (non-thrombocytopenic) and thrombocytopenic disorders.

Causes of non-thrombocytopenic purpura include:
Causes of thrombocytopenic purpura include:

These lists are far from exhaustive (see 'Associated diseases', below) but account for the more common causes.

Purpuric lesions can appear in normal patients, usually women. Bruises, either single or multiple, appear spontaneously, mainly on arms or legs, and resolve without any specific treatment. Senile purpura is usually seen on areas exposed to mild repeated trauma, such as the back of hands. Lesions keep their dark colour often for several weeks and there is no abnormality in bleeding times.

This will be guided by the differential diagnosis, much of which will already have been excluded.

  • FBC, ESR, platelets. The platelet count is fundamental. Leukaemia or related diseases may produce anaemia and leukocytopenia. ESR may indicate an inflammatory process. It is very nonspecific.
  • LFTs to check for liver disease.
  • A coagulation screen will screen for clotting factor deficiencies.
  • If the patient is on warfarin, check INR.
  • Plasma electrophoresis may show hypergammaglobulinaemia, paraproteinaemia and cryoglobulinaemia.
  • Autoantibody screen for connective tissue disorders.

The clinical condition may indicate further investigations, including blood culture and lumbar puncture.

These have been outlined in 'Differential diagnosis', above. Here are some points you may wish to bear in mind.

Bacterial infections

Those that cause purpuric rashes include meningococcal septicaemia, streptococcal septicaemia and diphtheria. Several acute viral infections also cause purpuric rashes. These include smallpox, chickenpox, measles, parvovirus B19 and haemorrhagic fevers caused by Ebola virus, Rift Valley virus and Lassa fever.

Allergic vasculitic purpura[7]

This is caused by inflammation and infiltration of the blood vessel wall as an anaphylactic reaction to a number of physical and chemical stimuli, including infections. Henoch-Schönlein purpura is one of the most common. Is often preceded by an upper respiratory tract infection due to beta-haemolytic streptococcal infection. It can occur in epidemics in young children with a fever followed by a purpuric rash, that may be slightly raised. Typically, it affects the fronts of the legs and the buttocks. There may be associated acute arthritis, gastrointestinal pain and nephritis with proteinuria. The rash may continue to form over several weeks. Serious acute complications include central nervous system (CNS) bleeding, acute intussusception or acute renal failure. Usually it is a self-limiting condition but it may respond to steroids.

Disseminated intravascular coagulation (DIC)[8]

There is massive ecchymosis with sharp, irregular borders of deep purple colour and an erythematous halo. It can evolve to haemorrhagic bullae and blue-black gangrene. These appear as multiple lesions, often symmetrically involving distal extremities, areas of pressure, lips, ears, nose and trunk.

Strong steroids

Long-term use of strong steroids can cause widespread purpura and bruising, normally on extensor surfaces of the hands, arms and thighs. It is caused by atrophy of the collagen fibres supporting blood vessels in the skin. A similar appearance is also found in senile-type purpura.

Blood transfusions[9]

Severe thrombocytopenia 5 to 12 days after receiving a blood product containing platelets is a rare complication, usually confined to multiparous[9] women. It is due to the production of an antibody to a specific platelet antigen that the woman normally lacks. The patient normally recovers within 1 to 3 weeks but the condition can be lethal and may need treatment with plasmapheresis or intravenous (IV) immunoglobulins.

Pigmented purpuric dermatoses

Pigmented purpuric dermatoses are a group of diseases characterised by erythrocyte extravasation - particularly in the lower limbs, associated with haemosiderin deposition. Think of these in chronic cases.


Both primary and secondary amyloid can cause purpura that is known as "pinch purpura" because of the typical appearance on the cheeks.

Factitial purpura[11]

This may be considered where there are episodes of inexplicable bleeding/bruising. They may represent severe emotional or psychiatric disturbance. They may also be a sign of abuse.

  • As purpura is a physical finding rather than a disease, the management is to make a diagnosis and to act accordingly. The management of the various diseases is found in the respective articles.
  • Purpura usually indicates a platelet count below 30 x 109/L and a serious haemorrhagic potential. A count of 20 x 109/L or less requires urgent treatment.[12]
  • If a child has bruising, check all over, including the anogenital area. Keep non-accidental injury in mind.
  • Never give an intramuscular (IM) injection if a serious bleeding disorder is suspected or a very painful haematoma will develop.
  • The glass test (diascope) is well known to patients and is very useful.

Further reading & references

  1. Purpura; University of Maryland Medical Centre
  2. Leung AK, Chan KW; Evaluating the child with purpura. Am Fam Physician. 2001 Aug 1;64(3):419-28.
  3. Purpura, DermNet NZ
  4. Purpura Rheumatica, DermIS (Dermatology Information System)
  5. Purpura Senilis, DermIS (Dermatology Information System)
  6. Purpura Steroidica, DermIS (Dermatology Information System)
  7. Saulsbury FT; Henoch-Schonlein purpura. Curr Opin Rheumatol. 2010 Sep;22(5):598-602.
  8. Becker J et al; Disseminated Intravascular Coagulation in Emergency Medicine, Medscape, Apr 2011
  9. Shtalrid M, Shvidel L, Vorst E, et al; Post-transfusion purpura: a challenging diagnosis. Isr Med Assoc J. 2006 Oct;8(10):672-4.
  10. Crookston K et al; Acquired bleeding disorders: AmyloidosisPathologyOutlines.com, 2010
  11. Yamada K, Sakurai Y, Shibata M, et al; Factitious purpura in a 10-year-old girl. Pediatr Dermatol. 2009 Sep-Oct;26(5):597-600.
  12. Silverman MA; Idiopathic Thrombocytopaenic Purpura, Medscape, Jan 2011

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS 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.

Original Author:
Dr Olivia Scott
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