Based on surverys of providers, vasculitis in children appears to have an incidence of about 50 cases per 100,000 children per year. Only HSP and KD are more common in children than in adults, with each one affecting at least 10-20/100,000 pediatric patients per year. Takayasu arteritis and ANCA-positive vasculiti-des, on the other hand, strike approximately one child in a million each year. Differences between adult and pediatric vasculitides are generally subtle, though they may have important implications. Since these conditions are so rare in the pediatric age group, diagnosis may be significantly delayed, leading to more disease-related damage at the time therapy is initiated. In addition, unlike adults, children may suffer irreversible effects on their physical and mental development both from the disease and from the medications used to treat it. On the other hand, children tend to have fewer comor-bidities and they are therefore more tolerant of potentially toxic therapies. This often results in better outcomes for children than adults, especially in conditions like Takayasu arteritis and PAN. Kawasaki disease (KD) has replaced acute rheumatic fever as the leading cause of acquired heart disease among children in developed nations. Since IVIG became the standard treatment for KD in 1986, the mortality rate of the disease has decreased from 1-2% to <0.1%, and the incidence of coronary artery aneu-rysms has decreased by 75%. Henoch-Schonlein purpura, also known as anaphylac-tic purpura, is a benign condition in the vast majority of affected children. Nonetheless, in rare cases, children affected by HSP may develop hypertension (especially during pregnancy) or renal failure long after the acute syndrome has resolved. One-third or more of children with PAN have the cutaneous form, largely limited to skin and joint involvement. While mortality is rare, aggressive control of the systemic inflammation and end-organ involvement is nonetheless needed if significant long-term morbidity is to be avoided.
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