What is in the Differential Diagnosis of Purpura?

Patient Presentation
A 2.5-year-old male came to clinic because of a new onset rash. The child had cold symptoms 2 weeks previously that had improved. He again began to have some rhinorrhea 2 days ago but was afebrile and otherwise well. That morning he awoke with a bright red rash on his extremities, trunk, buttocks and face that was slightly pruritic. His mother denied new soap/lotions, skin products, medications or complementary and alternative products or treatments. He was drinking well but eating less. There were several children at the daycare he attended who had recent colds. The past medical history showed a generalized rash to amoxicillin. The family history was negative for any autoimmune or kidney disease. The review of systems was otherwise normal.

The pertinent physical exam revealed normal vital signs including a temperature of 99.3°, blood pressure of 78/58, and growth parameters in the 5-15%. HEENT showed clear rhinorrhea. Lungs were clear. Extremities had no edema. His skin had bright red, uniform lesions that were generally well-demarcated without central clearing. The lesions were 1 cm with a great deal of coalescence. Some on the lower extremities felt slightly raised. The lesions were located on the face, extremities, buttocks and trunk and spared the scalp, genitals, hands, feet and intertrigenous areas. He had no mucous membrane involvement including his urethra. The diagnosis of a viral exanthem was made and the mother was instructed to monitor the child. She was told that it was possible that the pruritus could get worse and diphenhydramine could be used, as well as acetaminophen for discomfort.

The patient’s clinical course showed that on the early evening of the next day, the mother called because the boy’s rash on his legs was now purple and his feet had become swollen earlier in the day. She denied any other changes as to where the rash was located or how it looked other than that it was darker and more purplish. It was not “bumpier.” She denied any new “dots,” bleeding, oral lesions, eye changes, or edema of the face or hands. He continued to be afebrile, eating and drinking well. She had given him one dose of diphenhydramine earlier in the day. He had been acting normally during the day. The pediatrician who had seen the child was on call that evening and thought that this possibly could be Henoch-Schönlein purpura, but as the child was well, was drinking and urinating well, and had had a normal blood pressure the day before, he recommended to monitor closely the child for any changes and see the child the next day. The following day, the rash had begun to fade and was less pruritic. His blood pressure was normal. The purple changes that the mother had described were reproduced in the clinic when the child sat down. The lesions near the buttocks had a slightly darker hue to them that resolved when the child stood up. He had no edema on physical examination. The rash continued to fade over the next 2-3 days.

Children presenting with rashes are common but certain characteristics may be concerning such as descriptions of petechiae or purpura. Purpura are characterized by non-blanching skin lesions between 3-10 mm in size that are caused by bleeding into the skin. Usually they are reddish-purplish hence the name purpura coming from the Latin word. Non-blanching lesions that are 10 mm are ecchymosis.

Henoch-Schönlein purpura (HSP) is a generalized vasculitis that commonly involves the gastrointestinal tract, kidneys, skin and joints, and is especially seen in children 2-11 years old. Classically HSP presents with purpura of the lower-extremities (or other dependent areas), migratory polyarthritis, colicky abdominal pain, and renal disease. A macular-papular or urticarial rash can precede the purpura, but generally resolves within 24 hours such as the one above. Peripheral edema can occur because of the renal involvement. Its etiology is uncertain but is probably multifactorial with antigens, environmental and genetic factors. It is thought to be caused by an unknown antigen stimulating a rise in IgA producing and antigen-antibody complexes being deposited locally in the body and activating pathways leading to necrotizing vasculitis. Associations with bacteria, viruses, vaccinations and drugs have been reported. Most children have complete recovery but serious renal and gastrointestinal complications may occur.

Learning Point
The differential diagnosis of purpura includes:

  • Acute hemorrhagic edema of infancy – For more information about AHEI click here.
  • Acute streptococcal glomerulonephritis
  • Blood clotting disorders
  • Drugs – particularly which may cause fragile blood vessels or platelet problems
  • Hemolytic-uremic syndrome
  • Henoch-Schönlein or anaphalactoid purpura – for more information about HSP click here.
  • Hypersensitivity vasculitis
  • Hypertension – malignant, pre-eclampsia and similar gestational problems
  • Immune thrombocytopenic purpura
  • Infection
    • Disseminated intravascular coagulation / Sepsis
    • Purpura fulminans from Neisseria meningiditis
    • Congenital infections such as cytomegalovirus and rubella
    • Rickettsial diseases
  • Polyarteritis nodosa
  • Thrombotic thrombocytopenic purpura
  • Scurvy
  • Urticarial vasculitis
  • Trauma

Questions for Further Discussion
1. What causes urticaria?
2. What are the potential complications of HSP?
3. What are criteria for referral to a dermatologist?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Platelet Disorders and Vasculitis.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Weiss PF. Pediatric vasculitis. Pediatr Clin North Am. 2012 Apr;59(2):407-23.

Rigante D, Castellazzi L, Bosco A, Esposito S. Is there a crossroad between infections, genetics, and Henoch-Schonlein purpura? Autoimmun Rev. 2013 Aug;12(10):1016-21.

Mathur AN, Mathes EF. Urticaria mimickers in children. Dermatol Ther. 2013 Nov;26(6):467-75.

Roberts PF. Henoch-Schonlein Purpura. EPocrates Online. Available from the Internet at https://online.epocrates.com/u/2935110/Henoch-Schonlein+purpura/Diagnosis/Differential (rev. 7/8/13, cited 3/11/14).

MedlinePlus Encyclopedia. Purpura. Available from the Internet at http://www.nlm.nih.gov/medlineplus/ency/article/003232.htm (rev. 4/24/13, cited 3/11/14).

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Interpersonal and Communication Skills
    18. Using effective nonverbal, explanatory, questioning, and writing skills, the healthcare professional uses effective listening skills and elicits and provides information.

  • Systems Based Practice
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.


    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital