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Vasculitis, defined as inflammation of blood vessels, is a feature
of many rheumatic and nonrheumatic diseases of childhood. This chapter addresses
only those diseases in which vasculitis plays a central role in both
pathogenesis and clinical presentation. Criteria used for a diagnosis
of vasculitis in adults are often problematic when applied to children. Recently
a consensus was reached on a new international classification of
childhood vasculitis and these criteria will be used in this chapter.1 Classification
of vasculitis is based on the size of the blood vessels involved
or the pathology of the lesions (Table 203-1). This
chapter will be limited to the more commonly seen vasculitides of
childhood.
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Henoch-Schönlein purpura (HSP) is an
acute leukocytoclastic vasculitis, mainly affecting the small vessels
of the skin, joints, gastrointestinal tract, and kidneys (Table 203-2). HSP is the most common form
of systemic vasculitis in childhood with an incidence of about 10
cases per 100,000 a year. The main features of the disease include
nonthrombocytopenic palpable purpura (present in 100% of affected
children), arthritis or arthralgias (75–85%),
colicky abdominal pain with or without gastrointestinal hemorrhage
(60–85%), and renal involvement (10–50%).
The diagnostic criteria are shown in Table 203-2.
Although it can occur at any age, HSP is overwhelmingly a disease
of childhood. The mean age of patients is 6 years; 75% of
patients are younger than age 8 and 90% are less than 10
years of age. The clinical features of HSP may be atypical at the extremes of
age. The severity tends to be milder in infants under 2 years of
age and worse in adults. The disease is more common in males, although
sex differences are not seen in patients older than age 16.2 HSP
has a seasonal pattern, with peaks in winter and spring. It is an
IgA-mediated leukocytoclastic vasculitis, characterized by neutrophil
infiltration and fibrinoid necrosis in the vessel walls of arterioles,
capillaries, and postcapillary venules, with deposition of IgG,
IgA, and C3.3
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