Fibrillary glomerulonephritis is a rare cause of proteinuric kidney disease characterized by Congo red-negative fibrillary deposits and typically shows DNAJB9 positivity on immunohistochemistry. Amylo Show more
Fibrillary glomerulonephritis is a rare cause of proteinuric kidney disease characterized by Congo red-negative fibrillary deposits and typically shows DNAJB9 positivity on immunohistochemistry. Amyloidosis is defined by Congo red positivity and can be typed by laser microdissection-tandem mass spectrometry when routine studies are inconclusive. We report the case of a 64-year-old man with proteinuria and declining kidney function whose kidney biopsy showed DNAJB9-positive fibrillary glomerulonephritis in glomeruli, but Congo red-positive deposits confined to the medulla were DNAJB9 negative. Laser microdissection-tandem mass spectrometry of the medullary deposits identified apolipoprotein A-IV amyloidosis, establishing concurrent fibrillary glomerulonephritis and apolipoprotein A-IV amyloidosis in the same biopsy. Apolipoprotein A-IV amyloidosis is often medullary predominant and, in rare hereditary forms related to autosomal dominant Show less