Henoch-Schönlein Purpura (HSP) is an IgA-mediated, small vessel vasculitis that predominantly affects children. IgA, C3, and immune complexes deposit in arterioles, capillaries, and venules. It is important to differentiate this from IgA nephropathy where renal biopsies show similar pathology; however, IgA nephropathy mainly affects the kidneys of young adults. HSP can affect any organ system though the skin, gastrointestinal, and urinary systems are most common. Approximately 75% of cases occur in children between the ages of 2 and 11. About half of patients have had a preceding upper respiratory infection. The cause of HSP is unknown though there is some evidence to suggest that it may be of an infectious or drug-related etiology, as anti-streptolysin O titers are elevated in around 50% of patients. Children generally present with the classic rash described as non-blanching palpable purpuric lesions, with or without petechiae, on the lower extremities and buttocks.
So when should the emergency physician be concerned? Be sure to elicit a complete review of systems, and perform a full head-to-toe examination to identify other affected organ systems. Colicky abdominal pain and vomiting, with or without bloody stools, can be a sign of intussusception, which in HSP it is more often ileoileal versus the more common ileocolic. Arthralgias are also fairly common with HSP, occurring mainly in the knees and ankles. Acute scrotal pain and edema should make you think about testicular torsion, which is difficult to distinguish from HSP-related epididymoorchitis.
Laboratory analysis should include a urinalysis for blood and protein, indicating kidney involvement. If drawing blood, obtaining a blood urea nitrogen (BUN) and creatinine will establish baseline kidney function. You may want to order laboratory studies to rule out other potential diagnoses on your differential based on the patient's presentation, but they are not required to diagnose HSP. A normal platelet count helps to rule out thrombocytopenic causes of petechiae, such as idiopathic thrombocytopenic purpura (ITP), thrombotic thrombocytopenic purpura (TTP), and disseminated intravascular coagulation (DIC).
So now that you have established a diagnosis and have ruled out other dangerous diagnoses, what should disposition be for these children? Concern for intussusception or testicular torsion should prompt emergent imaging and consultation with your pediatric subspecialists or transfer to a facility where they are available. Ill-appearing children, or those with evidence of nephritis (hematuria, elevated creatinine, or hypertension), require consultation with your pediatric service and may require inpatient admission. Non-steroidal anti-inflammatory drugs (NSAIDs) are acceptable to use if there is no renal involvement. Advanced therapeutic regimens for severe HSP (steroids, IVIG, azathioprine, etc.) should be administered by an appropriate specialist outside of the ED setting. If the child appears otherwise well, as the vast majority will, discharge is safe with strict return precautions and close outpatient follow-up for weekly blood pressure checks and urine testing until told to stop by their pediatrician.
In conclusion, HSP is a relatively common disorder that you will encounter in your career. In about 95% of cases, the course is benign, and children do well with no long-term complications. Five percent of cases are complicated by long-term hypertension with less than 1% developing end-stage renal disease. The vast majority (greater than 75%) will have a single episode lasting 4-6 weeks without any later recurrence of symptoms. The emergency physician should be aware of the more serious complications of this disorder and arrange appropriate care and follow-up as indicated by the presenting clinical condition.
American Academy of Emergency Medicine. 2012;3(6) © 2012
American Academy of Emergency Medicine
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