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1 Minute Read: Purpuric Rash Symptoms and Its Differential Diagnosis

Posted by Jason Maude on Wed, Feb 15, 2012 @ 11:30 AM

Purpura is a purplish discoloration of the skin produced by small bleeding vessels under the skin surface which are also known as skin hemorrhages or blood spots. The appearance of purpura is striking, and it doesn’t blanch when pressure is applied, so it can also be known as a non-blanching petechial rash.  Purpuric rash can be further differentiated into the size of the lesions, petechiae are pinpoint hemorrhages less than 2mm in diameter, purpura are 2-10mm wide purple flat lesions and  purpuric ecchymosis are more than 10mm wide and look like a large bruised area. The rash can appear anywhere on the body.

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The bleeding can be caused by many different things, but one common explanation is due to thrombocytopenia -- the platelet count is so low that bleeding occurs or it can be caused by blood vessel damage.  Purpura is a clinical sign rather than a diagnosis, and therefore the patient should be examined for other signs and symptoms and a differential diagnosis should be constructed, as there can be many causes including meningococcal disease, disseminated intravascular coagulation and vasculitis syndromes.  It is worth considering the differential classified into vascular and thrombocytopenic causes.

Some self-limiting causes of petechiae around eyes, mouth or head could be due to excessive vomiting or coughing, but other symptoms should be examined.  Further history taking, examination and lab testing will aid the narrowing of the differential diagnosis.   Tests to consider include a full blood count, platelet count, prothrombin and bleeding time.

Purpuric rash causes for consideration in your differential diagnosis work up can be seen by using Isabel in this case with a child aged 6-12 years.

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Topics: diagnosis decision support, Differential diagnosis

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