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Collagenofibrotic glomerulopathy is a rare renal disease, first described by Arakawa in 1979. Fewer than 50 cases have been reported in literature. It occurs more frequently in adult Indian population in a sporadic manner. In normal human kidney, type III collagen is present in the interstitium and blood vessels. Collagenofibrotic glomerulopathy is characterised by accumulation of type III collagen in the glomerular mesangial and subendothelial areas.
Collagenofibrotic glomerulopathy may present as an isolated, sporadic form in adults or as an autosomal recessive pattern in children. Patients present with proteinuria, most often in the nephrotic range and microscopic haematuria and usually have a progressive decline in renal function.
This case report serves as a reminder for practicing nephrologists and renal pathologists to consider this disease entity in the differential diagnosis of fibrillary glomerulopathy.
CASE- 56-year-old male, known case of hypertension for the past 12 years, presented with raised serum creatinine on routine evaluation, with a positive family history of chronic kidney disease in brother. His investigations revealed serum creatinine – 1.39mg/dl, urine routine – protein 10- 20mg/dl, no RBCs, urine albumin creatinine ratio – 68mg/g. His serum creatine further increased to 1.5mg/dl and native kidney biopsy was performed.
Biopsy revealed 10 glomeruli, all non-sclerosed with mesangiocapillary pattern of glomerular injury due to deposition of PAS negative material in the expanded mesangium and along the capillary loops. Presence of subendothelial expansion due to similar material. Electron microscopy revealed marked expansion of the subendothelial and mesangial space by deposition of exogenous material, which had a disorganised appearance and was composed of curvilinear structures indicative of Type III collagen deposition. The higher magnification of the collagen fibrils showed banded appearance. Features were consistent with collagenofibrotic glomerulopathy.
The patient was managed on antihypertensives- angiotensin receptor blocker and calcium channel blocker.
Collagenofibrotic glomerulopathy is an idiopathic glomerular disease characterised by massive accumulation of type III collagen fibrils within the mesangial matrix and subendothelial space. Type III collagen is a homotrimer of three identical alpha chains. It is synthesized as a large precursor molecule, type III procollagen, which undergoes enzymatic cleavage of its N terminal peptide to form type III collagen.
These patients present with hypertension, which is an early feature along with pedal oedema. Patients have proteinuria, that may reach nephrotic range in about 60% of the patients. The disease is almost always progressive.
Electron microscopy is imperative to establish a definitive diagnosis. The extracellular space of the mesangium and subendothelial are expanded with accumulation of fibrillar material. These fibres have curved or frayed appearance, and have a transverse band structure, with a distinctive periodicity of 60nm.
There is no specific treatment for this disease. Supportive measures include control of hypertension and diuretics to relieve oedema. Patients may require renal replacement therapy or transplantation if patients reach end stage renal disease. No recommendations have been made on the use of steroids