A 29-year-old man had oedema, proteinuria in nephrotic range, haematuria and cardiac arrhythmia (second grade atrioventricular block). The pathologic findings of kidney biopsy showed in light microscopy diffuse mesangial matrix increase with mild mesangial proliferation and variable thickening of the glomerular capillary walls. IgG, c3 and c1q were intensely fluorescent and exhibited a diffuse granular pattern in mesangial areas and along the capillary walls. Both kappa and lambda chains were weakly positive in the same pattern. Ultrastructurally, microfibrils of about 20 nm in width were seen to be deposited in mesangial areas and along the glomerular basement membranes. Congo red stain and metachromasia were negative. Neither cryoglobulinaemia nor paraproteinaemia including light chains were found. The aetiology of nonamyloidotic fibrillary glomerulopathy is unknown and no clear-cut clinical or pathologic pattern has emerged. It may represent more than one disease process with a common morphologic expression.23295-301