C1q nephropathy with asymptomatic urine abnormalities.

We found four cases of C1q nephropathy (C1qN) among a total of 193 pediatric series of first renal biopsies. Among them, 94 biopsies were performed because of asymptomatic urine abnormalities detected by school urinary screening program in Japan; three cases out of these 94 biopsies (3.2%) met the criteria of C1qN. One case out of the remaining 99 biopsies with symptomatic renal diseases (1%) also met the criteria of C1qN. Three cases with asymptomatic onset presenting with mild proteinuria with or without hematuria equally showed histologic features of membranoproliferative glomerulonephritis and showed improvements in urinalysis without corticosteroid treatment. Our data suggest that membranoproliferative glomerulonephritis may be a common histological feature of asymptomatic pediatric C1qN in Japan and that this type of glomerulopathy may follow a relatively good clinical course without steroid therapy.