Two cases of atypical membranoproliferative glomerulonephritis showing opposite clinical course

Atypical membranoproliferative glomerulonephritis (MPGN) is considered to progress to typical MPGN, and it is believed that it can be treated with corticosteroids. However, consensus that atypical MPGN is a continuum of morphologic manifestations of typical MPGN cannot be reached. Herein, we report two cases of atypical MPGN with opposite clinical course. Case 1 was a 4-year-old boy with macrohematuria and proteinuria with no prodromal symptoms. His serum C3 level had abruptly dropped, and renal biopsy confirmed a diagnosis of atypical MPGN. After performing kidney biopsy, his urinary abnormality improved and his C3 level had normalized 1 year after onset without medication. At the most recent follow-up, neither proteinuria nor hematuria was detected. Case 2 was a 7-year-old girl with microhematuria and proteinuria at her school urinary screening. Her first biopsy finding was similar to dense deposit disease, and the second biopsy showed atypical MPGN. Oral corticosteroids were started from this point, but heavy proteinuria and hypocomplementemia could not be improved sufficiently. We immediately performed third kidney biopsy and diagnosed typical MPGN. These findings suggest that the indication of therapy for atypical MPGN should be re-examined. Aggressive therapy such as steroid administration is not necessarily essential and effective for therapeutic intervention of all atypical MPGN. Moreover, atypical MPGN may involve different etiologic and pathogenetic factors, rather than a continuum of morphologic manifestations of MPGN.