Histological patterns of steroid resistant nephrotic syndrome in bulgarian children: a single centre study

Nephrotic syndrome is the most frequent glomerular disease in childhood. Steroid resistant nephrotic syndrome (SRNS) represents about 20% of children with nephrotic syndrome. SRNS is one of the leading indications for perform-ing renal biopsy in children. The objective of this retrospective study is to determine the histological patterns of SRNS in Bulgarian children and to com-pare them with the worldwide findings. The study included 49 patients with SRNS. All biopsies were performed at the Department of Pediatric Nephrology and Dialysis, University Children's Hospital, Sofia, Bulgaria between January 2004 and January 2020. The renal biopsies were examined histologically and with immunohistochemistry at the Pathology Department, Military Medical Academy, Sofia and Medical University - Sofia, Bulgaria. Twenty-eight boys (57.1%) and 21 girls (42.9%) were included in the study. The age at diagnosis ranged from 8 months to 212 months (17 years and 8 months) with a mean of 94 months (7 years and 10 months). Generalized edema was the most common presentation - 55.1%, followed by microhaematuria - 53.1% of cases. Histo-logical examination revealed several different forms: Focal segmental glomeru-losclerosis (FSGS) in 30.6% (n = 15), Mesangial proliferative glomerulonephri-tis (MesPGN) in 14.3% (n = 7), Membranous glomerulonephritis (MGN) in 12.2% (n = 6), IgM nephropathy in 12.2% (n = 6), Membranoproliferative glomerulonephritis (MPGN) type I in 8.2% (n = 4), C3 glomerulopathy 8.2% (n = 4), Minimal change disease (MCD) in 4.1% (n = 2), IgA glomerulonephri-tis in 4.1% (n = 2), Diffuse mesangial sclerosis (DMS) in 4.1% (n = 2) and C1q nephropathy in 2.0% (n = 1). Although SRNS in Bulgarian children might represent a broad spectrum of glomerular diseases it could be attributed in approximately two/third of patients to four of them - FSGS, MesPGN, MGN, and IgM nephropathy.