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Patient Story
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A previously healthy 11-year-old girl presents to her pediatrician with a rash on her legs and knee pain. She admits to having abdominal pain the day before but her stomach is feeling better today. She denies fever, nausea, vomiting, and diarrhea. The right knee hurts sufficiently that she has been limping since she woke up. Upon exam the child is afebrile and does not appear to be in distress. She has an impressive rash on her legs with right knee swelling (Figure 153-1). The rash is petechial and purpuric and slightly palpable. The linear pattern running down the thigh matches the seams of her pants. A urinalysis performed in the office reveals blood in the urine but no protein. The pediatrician diagnoses Henoch Schonlein purpura (a type of vasculitis) and discusses the treatment plan with the girl and her mother.

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FIGURE 153-1

Henoch-Schönlein purpura in an 11-year-old girl. A. In addition to the palpable purpura, this patient also had abdominal pain. Note how the seam of her jeans is visible in the purpuric pattern. B. She also had knee pain and swelling and was walking with a limp. (Used with permission from Richard P. Usatine, MD.)

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Introduction
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Vasculitis refers to a group of disorders characterized by inflammation and damage in blood vessel walls. They may be limited to skin or may be a multisystem disorder. Cutaneous vasculitic diseases are classified according to the size (small versus medium to large vessel) and type of blood vessel involved (venule, arteriole, artery, or vein). Small and medium-size vessels are found in the dermis and deep reticular dermis, respectively. The clinical presentation varies with the intensity of the inflammation, and the size and type of blood vessel involved.1 Hypersensitivity vasculitis (HSP) is also known as leukocytoclastic vasculitis. HSP is a type of leukocytoclastic vasculitis.

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Epidemiology
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  • HSP (Figures 153-1 to 153-3) occurs mainly in children with an incidence of approximately 1 in 5000 children annually.2 It is the most common vasculitis in the pediatric population.3

  • Although HSP affects all age groups, it is most common in children ages 2 to 6 years old.35 The disease affects an estimated 70.3 per 100,000 children per year with a male to female ratio of 1.2:1.3,4

  • White children have a much higher incidence of HSP compared to black children.3,4

  • Although the incidence in children has been reported to be about 100 times greater than adults, HSP is typically less severe in the pediatric population.6

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FIGURE 153-2

Henoch-Schönlein purpura presenting as palpable purpura on the lower extremity. The visible sock lines are from lesions that formed where the socks exerted pressure on the legs. (Used with permission from Richard P. ...

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