Classification and pathogenesis of arteritis in children.

Systemic necrotizing vasculitis in children is a rare but serious disorder. During the past 25 years, 121 children within this disease category have been referred to the Hospital for Sick Children, London (HSC). Classification is difficult but the largest subgroups identified were polyarteritis nodosa (PAN)--29 children and Kawasaki syndrome (KD)--42 children. In spite of modern therapy including steroids, cyclophosphamide, anti-platelet medication, plasma exchange, prostacyclin, high dose gamma globulin and cyclosporin, mortality remains high. Overall mortality for HSC patients was 12% (66% for pulmonary vasculitis, 21% for PAN, and 2% for KD). Recent advances are beginning to shed some light on the etiology and pathogenetic mechanisms involved in PAN and KD. There is now good evidence to support roles for platelet immune complex interactions, anti-neutrophil cytoplasmic antibodies, and anti-endothelial cell antibodies in the pathogenesis. It seems likely that, in KD at least, retroviruses may have an etiological role either by directly infecting endothelial cells or indirectly via T-cells, antibody, or immune complex formation.