Membranoproliferative glomerulonephritis and C3 glomerulonephritis: frequency, clinical features, and outcome in children.

C3 glomerulonephritis (C3GN) is a recently described disease that is related to membranoproliferative glomerulonephritis (MPGN). We retrospectively compared the frequencies, clinical characteristics, treatment modalities, and outcomes of C3GN and MPGN in a cohort of Japanese children. Children who were pathologically diagnosed with MPGN (type I or III) in our hospital were divided into two groups based on immunofluorescence imaging of renal biopsies: children with MPGN induced by classical complement pathway activation (classical MPGN) and children with C3GN. Of 14 children with MPGN (five boys), four had classical MPGN, eight had C3GN, and two had unclassifiable glomerulonephritis. Four children with classical MPGN and seven with C3GN received methylprednisolone pulse therapy followed by oral prednisolone for 2 years (MPT+PSL therapy). Subsequently, six of seven children with C3GN received combined therapy (prednisolone, azathioprine, and anticoagulants) for 2 years because they responded poorly to MPT+PSL therapy. At the last follow-up visit, two children with classical MPGN and seven with C3GN had not achieved remission. One child with classical MPGN and five with C3GN had hypocomplementaemia at the last follow-up. None of the children had renal impairment. More than half of the patients previously diagnosed with MPGN fulfilled the criteria for C3GN in children. C3GN may be more refractory than classical MPGN to immunosuppressant therapy.