OBJECTIVEAntineutrophil cytoplasmic antibody (ANCA) associated small vasculitides (ASV) are rare in children and often complicated in clinical manifestations and have very poor prognosis. In order to deepen our understanding of ANCA-associated small vasculitis (ASV) in children, the present study aimed to characterize their clinical manifestations, serum ANCA and renal histopathological findings and outcomes in Chinese children.

METHODSSerum ANCA was qualitatively tested with indirect immunofluorescence microscopy and anti-proteinase 3 (PR(3)) and anti-myeloperoxidase (MPO) activity were quantitated by enzyme-linked immunosorbent assays (ELISA), and renal biopsies were done to investigate the pathological changes. The clinical manifestation, serum ANCA and renal histopathological findings and outcome were characterized in 5 children with ANCA associated small vasculitis.

RESULTS(1) Five children with ANCA associated small vasculitis only accounted for 1.20% of children in whom renal biopsy was performed and 0.25% of hospitalized children with renal diseases during the same period. The age of onset of the 5 children with ASV was between 8 to 12 years with mean age 10.5 years. All ASV children were female. (2) All ASV children were negative for C-ANCA and showed normal anti-proteinase 3 activities, but positive for P-ANCA with high anti-myeloperoxidase activities between 98 to 242 kEU/L. The mean value of MPO-ANCA was 154.5 kEU/L (normal range < 12.7 kEU/L). (3) All ASV in the children was microscopic polyarteritis with wide-spread glomerular crescents formation and capillary tuft fibrinoid necrosis. Variety of complement C3 deposits and weak immunoglobulin deposits were noted in all ASV but one child who showed relatively strong deposits of IgA and IgM. The electronic dense deposits were mainly located in subendothelial space but were also found in the glomerular basement membrane in one child. (4) Three children with ASV died within one year after diagnosis, and two got remission and restored renal function after combined pulse therapy with methylprednisolone and cyclophosphamide (CTX), but remained to have hematuria and small amount of proteinuria after 1 and 5 year follow-up, respectively.

CONCLUSIONChildhood ASV was female and P-ANCA predominant, more vulnerable to progress to renal failure and poorer in prognosis than adult cases. Qualitative and quantitative ANCA measurement and renal biopsy were key to the diagnosis of ASV in children.