What is your diagnosis?
The light microscopic image depicts a glomerulus with collapse of the capillary loops on the Jones methenamine silver stain. This lesion is identified by its prominent capillary loop collapse with overlying epithelial cell hyperplasia and hypertrophy, with associated protein resorption droplets. It is important to look at the background tubulointerstitium for findings that can be seen in association with this lesion such as increased proximal tubular resorption droplets, tubular microcystic tubular dilatation, and interstitial inflammation, as this lesion can be easily mistaken for crescent formation. Collapsing glomerulopathy can be seen as a primary (idiopathic) disease as well as secondary to infections (HIV, Parvovirus, and CMV), autoimmune disease, and increased interferon states. It has also be strongly associated with mutations in the G1/G2 risk alleles of the APOL1 gene within African Americans, specifically those of West African descent. The case presented here is from a transplant patient who subsequently developed collapsing glomerulopathy after infection with SARS-CoV-2. A recent case report has identified collapsing glomerulopathy in a patient with recent COVID-19 infection (see reference).
Larsen CP, et al. Collapsing Glomerulopathy in a Patient with COVID-19. Kidney Int Rep (2020) 5: 935-939.
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