Is There Any Association Between IgAN and Fibrillary Glomerulonephritis?

Introduction: Fibrillary Glomerulonephritis is a rare form of non amyloid fibrillary glomerular deposition disease typically affecting adults aged 41 to 80 years old. This condition can present with hematuria, proteinuria, and signs of renal insufficiency. In this report we present a case of fibrillary glomerulonephropathy with mild activity and mild chronicity in a patient with a history of IgA nephropathy 12 years prior in remission Case Description: A 70 year old female with past medical history including chronic kidney disease stage 3B due to IgA nephropathy/ Henoch-Schönlein purpura in remission with baseline cr of 2 mg/dl, atrial fibrillation, hypertension, and type 2 diabetes mellitus presented to the outpatient nephrology clinic for management of acute kidney injury. She has a history of biopsy proven IgA nephropathy/ Henoch-Schönlein purpura 12 years ago she was treated with steroids in remission. Upon clinic visit, her serum creatinine was 2.5mg/dl, her spot protein creatinine ratio revealed 0.5 gm protein which was at her baseline with hx of IgA nephropathy. The patient did not report any NSAID use, antibiotic use and over the counter medication use. Given the unexplained raise in creatinine we performed a repeat renal biopsy which showed diffuse mesangial proliferative glomerulonephritis consistent with fibrillary glomerulonephritis, tubular atrophy with fibrosis. Discussion: Fibrillary glomerulonephritis and IgA nephropathy are distinct glomerular diseases with different pathologic and immunopathologic features, and there is no established direct association between the two entities. Fibrillary glomerulonephritis is characterized by the deposition of nonbranching fibrils which are typically IgG in origin. In contrast IgA nephropathy is characterized by the deposition of IgA and complement C3 in the mesangium. This case potentially highlights an incidental finding of fibrillary glomerulonephritis on repeat biopsy in a patient with known history of IgA nephropathy. While both conditions involve glomerular injury by immunoglobulins, their pathogenesis and histologic characteristics are distinct. Any association between these two conditions is yet to be determined.