IT IS NOT ALWAYS DIABETIC NEPHROPATHY: A CASE REPORT OF FIBRILLARY GLOMERULONEPHRITIS

Introduction:

The prevalence of non-diabetic renal disease in patients with type 2 diabetes mellitus is ranging from 13% to 53%. Infection-related glomerulonephritis is the most common diagnosis (50%), followed by membranous nephropathy (15%), pyelonephritis (10%), and focal segmental glomerulosclerosis (10%). It is important to note that proteinuria does not necessarily signify diabetic nephropathy in the context of diabetes mellitus.

Fibrillary glomerulonephritis (FGN) is a rare proliferative form of glomerular disease with less than 1% incidence in native renal biopsy. It was initially thought to be idiopathic, but recent studies show an association with autoimmune disease, malignancy, and hepatitis C infection. FGN is defined by the ultrastructural finding of organised, randomly arranged, non-branching fibrils confined to the glomeruli. The mean diameter of the fibrils is 20 nm (range 15-25 nm). Immunofluorescence shows strong staining of IgG, C3, Kappa &Lambda. In 2018, DNAJB9 was identified as one of the most abundant glomerular proteins in the FGN, making a diagnosis possible without a kidney biopsy.

Methods:

A 53-year-old male known to have diabetes mellitus type 2 for twenty years on insulin therapy, diabetic non-proliferative retinopathy, hypertension, chronic kidney disease stage 3 and benign prostatic hyperplasia. He presented to the nephrology clinic for follow-up of chronic kidney disease. He had nephrotic range proteinuria. The examination was remarkable for bilateral pitting lower limb oedema. Laboratory investigations showed creatinine of 254 mmol/L, Urea 12, HbA1C 8.9 %. Serum protein electrophoresis confirmed the absence of an M band and a negative autoimmune and viral hepatitis panel. Urine analysis showed microscopic hematuria with urine RBCs > 100 and 3+ protein. The 24-hour urine protein was 4.9 g/g. US KUB showed normal-sized bilateral kidneys with maintained corticomedullary differentiation and increased echogenicity.

Results:

A kidney biopsy was obtained. The glomeruli show focal segmental and global endocapillary proliferation with mesangial immunoreactivity to IgM, IgG, IgA and C3 consistent with focal proliferative glomerulonephritis. The glomeruli show diffuse mesangial proliferation with significant glomerular enlargement, hyalinization of arterioles, significant tubular atrophy and interstitial fibrosis and inflammation consistent with diabetic nephropathy. Electron microscopy showed fibrillary material deposition in the mesangium; their diameter range is 7.376 -16.495 nm. They are non-branching and haphazardly arranged. The Congo red stain was negative. The differential diagnosis includes diabetic fibrillosis and fibrillary glomerulonephritis.

Conclusions:

The patient's follow-up was intended to slow the progression of chronic kidney disease by managing diabetes and hypertension. The patient was given a trial of low-dose steroids and Mycophenolate mofetil (MMF) 1 g twice daily. Unfortunately, after seven months, the patient reached end-stage renal disease (ESRD) and underwent a live unrelated kidney transplant. Following the transplant, the patient's allograft function was stable, and there was no recurrent proteinuria. The prognosis of fibrillary glomerulonephritis is usually poor, with a median time to reach ESRD being two years +/- 15 months. Currently, there is no established standard therapy for FGN. Some studies have raised doubts about the benefits of rituximab, particularly in cases with relatively normal baseline kidney function. Ongoing research is investigating the potential of different immunosuppressive treatments, including steroids, cyclophosphamide, rituximab, and cyclosporine. The risk of recurrence after kidney transplantation is as high as 50%.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.