ABMR, ALECT, and Fibrillary Glomerulopathy

Welcome back to another interesting case in our Banff and Beyond series. To begin, the history is a 59 y/o white male status post-second transplant, living unrelated Hispanic donor, who presents with proteinuria with a UPCr ~7 g/g and an elevated creatinine: 1.56 mg/dL. At low power, we can see we have a good biopsy with cortex, and the minor interstitial inflammation appears confined to areas of prior scarring albeit occasional intact tubules show mild tubulitis. As we examine glomeruli, we can see that we have segmental glomerulitis in approximately 25-75% of intact glomeruli (G-2), and as we move to peritubular capillaries, we also have moderate peritubular capillaritis (PTC-2) and thus overall have moderate microvascular inflammation. These findings in conjunction with our positive C4d stain, are compatible with active antibody-mediated rejection. However, our case continues with other findings as we can see moderate mesangial matrix expansion that is non-argyrophilic via the silver stain with extension into capillary loops. Moving back to our immunofluorescence we can see that there is smudgy mesangial and capillary loop staining with IgG, C3, kappa, and lambda light chains. By electron microscopy, we can see that the mesangium and capillary loops show randomly arranged fibrils ~ 20 nm which our DNAJB9 stain confirms as Fibrillary glomerulopathy. Finally, our third and final finding in this biopsy is patchy interstitial staining which shows characteristic “apple green” birefringence under polarized light via Congo red, compatible with amyloid and which was found to be ALECT2. For this case, we have not only active antibody-mediated rejection but also recurrent fibrillary glomerulopathy as well as ALECT2 amyloidosis. Thanks everyone, and see you next time!