Collagenofibrotic (Collagen Type III) glomerulopathy in association with diabetic nephropathy

Collagenofìbrotic (collagen type III) glomerulopathy (CG) is a rare nonimmune-mediated glomerular disease. It is characterized by massive deposition of organized collagen type III fibers, which is localized in the mesangial and subendothelial glomerular areas and associated with increased serum levels of procollagen type III peptide. Association with systemic diseases and malignancies is extremely rare. Herein, we present a case of a nine-year-old girl, known case of type I diabetes mellitus, who presented with fever, nephrotic range proteinuria, generalized edema, and hypertension. Clinical examination did not show nail abnormalities or bone abnormalities. Renal biopsy revealed mesangial expansion and remarkable narrowing and obliteration of the glomerular capillaries by pale, amorphous material. Immunohistochemical study demonstrated diffuse linear glomerular capillary and tubular basement membrane staining for immunoglobulin G (IgG) and albumin. Ultrastructural examination identified massive mesangial and sub-endothelial deposition of dense frayed, curvilinear banded fibers with characteristic features of type III collagen. The patient was diagnosed to have combined CG and diabetic nephropathy (DN). This is the first report of CG in association with diabetic changes in renal biopsy. In this report, we describe the clinicopathological characteristics of this disease, review CG in pediatric population, and explore its association with DN.