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A previously healthy 8-year-old boy presented with 2 days of knee and ankle pain with no known cause. His parents denied that he had any trauma or fever. On physical examination, he was afebrile in no apparent distress. His left knee was swollen and tender (Figure 175-1). He admitted to other joint pains but there was no swelling or tenderness in the other joints. The pediatrician noted a petechial and purpuric eruption from his buttocks down to his ankles (Figure 175-1). It was non-blanching but only barely palpable. There were prominent circumferential petechiae around the left sock area. Upon further questioning, the mother admitted that her son had a viral upper respiratory infection 2 weeks ago. A urinalysis showed mild hematuria but no proteinuria. He never developed abdominal pain. Therapy was supportive and systemic corticosteroids were not used.
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Henoch-Schonlein Purpura (HSP) is a small vessel vasculitis characterized in children by a classic, palpable, purpuric rash over the lower extremities. In addition to the rash, children may also exhibit arthralgias, hematuria, and abdominal pain. The exact disease trigger is unknown; however, the symptoms of HSP are attributed to IgA deposition in the systemic vasculature. Though a minority of patients may develop long-term renal complications, the majority of cases are self-limited.
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In the early 20th century, HSP was thought to be due to anaphylaxis. Consequently, the disease was named “anaphylactoid purpura.” Occasionally, this term may still be used in reference to HSP.1
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HSP is the most common vasculitis in the pediatric population.2
Although HSP may affect all age groups, it is most common between children ages 2 to 6 years old.2–4
The disease affects an estimated 70.3 per 100,000 children per year.2,3
A very slight male predominance exists with a 1.2:1 male to female ratio.2,3
White children have a much higher incidence compared to black children.2,3
Though the incidence has been reported to be about 100 times greater in children than adults, HSP is typically less severe in the pediatric population.5
The peak disease occurrence is in the fall and winter months.1
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Etiology and Pathophysiology
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