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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.

Table 203-1. Proposed Classification of Childhood Vasculitis (International Consensus Conference, Vienna 2005)

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

Table 203-2. Classification Criteria for Henoch-Schönlein Purpura

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