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Background: Segmental glomerulosclerosis without significant mesangial or endocapillary proliferation is rarely seen in IgA nephropathy (IgAN), which simulates idiopathic focal segmental glomerulosclerosis (FSGS). We recently recognized aberrant blood vessels running through the adhesion sites of sclerosed tufts and Bowman's capsule in IgAN cases with mild glomerular histologic change. Methods: To characterize aberrant blood vessels in relation to segmental sclerosis, we retrospectively reviewed the clinical and histologic features of 51 cases of FSGS-like IgAN and compared them with 51 age and gender-matched idiopathic FSGS cases. Results: In FSGS-like IgAN, aberrant blood vessel formation was observed in 15.7% of cases, 1.0% of the total glomeruli, and 7.3% of the segmentally sclerosed glomeruli, significantly more frequently than in the idiopathic FSGS cases (p = .009). Aberrant blood vessels occasionally accompanied mild cellular proliferation surrounding penetrating neovessels. Clinically, all FSGS-like IgAN cases had hematuria; however, nephrotic range proteinuria was significantly less frequent than idiopathic FSGS. Conclusions: Aberrant blood vessels in IgAN are related to glomerular capillary injury and may indicate abnormal repair processes in IgAN.
Key Words: Glomerulosclerosis, focal segmental; Glomerulonephritis, IgA; Kidney glomerulus; Neovascularization
IgA nephropathy (IgAN) is characterized by dominant or codominant IgA deposits in the mesangial matrix and is usually accompanied by focal or diffuse mesangial proliferation. However, IgAN has a variety of histologic features ranging from normal to minimal glomerular alterations to diffuse endocapillary and crescentic glomerulonephritis.
Glomerular segmental sclerosis is not unusual in biopsy samples that are diagnosed as IgAN, but it is usually associated with severe mesangial proliferation and/or advanced tubulointerstitial fibrosis.1,2 Haas3,4 reported a form of segmental sclerosis in IgAN that did not accompany mesangial proliferation and demonstrated clinical features that were indistinguishable from idiopathic focal segmental glomerulosclerosis (FSGS). Of the 18 cases presented in his study, 82% had nephrotic syndrome and all but one case had favorable prognoses. Another description of segmental sclerosis without significant mesangial proliferation was reported by Weber et al.2 In their series of 26 cases, nephrotic syndrome was present in 24%, diffuse effacement of foot processes in only one case and the clinical outcomes were worse than in cases without FSGS. These two contrasting studies suggest that cases of mild IgAN with FSGS that are morphologically similar but have different pathogeneses may have different clinical outcomes....