Four cases of type III collagen deposition glomerulopathy and summary of the literature.

Collagen type III glomerulopathy is a rare glomerular disorder characterized by the deposition of type III collagen fibers within the glomeruli, predominantly in the mesangial and subendothelial regions. Renal biopsy with histopathological examination remains the gold standard for diagnosis of this disease. Clinically, collagen type III glomerulopathy typically presents with proteinuria and progressive renal dysfunction, with or without nephrotic syndrome. Collagen type III glomerulopathy affects individuals across all age groups, ranging from children to adults, and shows no apparent sex predominance. This study retrospectively analyzed four patients with collagen type III glomerulopathy diagnosed at the First Affiliated Hospital of Wenzhou Medical University between 2011 and 2024 and reviewed 105 cases reported worldwide in the English-language literature. All patients presented with proteinuria, and half had renal impairment. Electron microscopy consistently demonstrated abnormal collagen fibrils in the mesangial region. Over a median follow-up of 71.5 months, half of the patients with available follow-up data progressed to end-stage renal disease, whereas the remaining patients maintained stable renal function after intervention. Globally, reported collagen type III glomerulopathy cases exhibited heterogeneous clinical presentations, and current data support an association between nephrotic-range proteinuria and poorer renal outcomes.