++
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 establishing a diagnosis of vasculitis in adults are often problematic when applied to children. Recently, a consensus was reached on a new classification of vasculitis, and these criteria will be used in this chapter. Classification of vasculitis is based on the size of the blood vessels involved or the pathology of the lesions (Table 200-1). This chapter will be limited to the more commonly seen vasculitides of childhood.
++
+++
HENOCH-SCHÖNLEIN PURPURA (IGA VASCULITIS)
++
Henoch-Schönlein purpura (HSP), recently renamed IgA vasculitis, is an acute leukocytoclastic vasculitis, affecting mainly the small vessels of the skin, joints, gastrointestinal tract, and kidneys. HSP is the most common form of systemic vasculitis in childhood, with an incidence of about 10 cases per 100,000 per 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 200-2. 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 younger than 10 years of age. The clinical features of HSP may be atypical at the extremes of age, typically presenting with milder manifestations in infants younger than 2 years of age and a more severe course in adults. The disease occurs more frequently in males, although sex differences are not seen in patients older than age 16 years. 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 walls of arterioles, ...