August 22, 2017
IgA and APOL1
The presence of two APOL1 risk alleles, which predominantly affects population of recent African ancestry, confers up to 29x increased risk for renal disease. The morphologic manifestation of APOL1-associated nephropathy is quite variable, and includes focal segmental glomerulosclerosis (FSGS), collapsing glomerulopathy and non-specific glomerular and tubulointerstitial arterionephrosclerosis-like chronic changes (see reference). In order to develop renal disease, it is believed that carriers of two APOL1 risk alleles required either additional genetic alterations that contribute to the disease, or additional environmental risk factors. Some of these known factors include HIV infection, sickle cell disease, systemic lupus erythematosus and membranous glomerulopathy, among others. The biopsy shown is from a 25 year old African American patient who presented with hematuria, proteinuria and chronic kidney disease. The morphologic changes are diagnostic of IgA nephropathy (Figures 1, 2 and 3). However, the biopsy also showed frequent disappearing and solidified-type globally sclerotic glomeruli along with early microcystic tubular dilatation (Fig 4 and 5). Subsequent genetic testing showed the presence of two APOL1 risk alleles which is indicative of concurrent IgA and APOL1-associated nephropathy.
Reference: Larsen CP, Beggs ML, Saeed M, et al. Histopathologic findings associated with APOL1 risk variants in chronic kidney disease. Mod Pathol 2015; 28: 95-102