FSGS Flashcards
FSGS
Background
FSGS is the most common cause of nephrotic syndrome in African American adults and most common cause of GN-related ESRD in Black and White patients in the United States.
FSGS
Background
FSGS refers to a morphologic pattern of glomerular injury that may arise from a primary podocytopathy or secondary adaptive process involving nephron mass reduction, reflux nephropathy, viral or drug toxicity, genetic mutations, or other glomerular disease.
FSGS
Background
Histopathologic findings: segmental increase of mesangial matrix with obliteration of capillaries, sclerosis, hyalinosis, foam cells, podocyte hypertrophy with or without hyperplasia, and adhesions between glomerular tuft and Bowman capsule.
FSGS
Background
NOTE:
The deep inner juxtamedullary glomeruli are preferentially affected in early primary FSGS. Renal biopsies containing <15 glomeruli or only cortical glomeruli cannot exclude FSGS.
FSGS
Classification of FSGS
FSGS arising from primary alteration of glomerular epithelial cell:
Occurs with podocytopathies (e.g., genetic disorders), drugs, viral infections and primary FSGS. See Etiologies of FSGS below.
FSGS
Classification of FSGS
FSGS arising from primary alteration of glomerular epithelial cell:
Sudden onset edema and proteinuria
FSGS
Classification of FSGS
FSGS arising from primary alteration of glomerular epithelial cell:
Nephrotic syndrome (proteinuria > 3.5 g/d and serum albumin < 3.5 g/dL)
FSGS
Classification of FSGS
FSGS arising from primary alteration of glomerular epithelial cell:
Widespread foot process effacement of nonsclerotic glomeruli on EM
FSGS
Classification of FSGS
FSGS arising from reduced nephron mass or glomerular adaptations to injurious insults.
Development of edema and proteinuria are usually slowly progressive.
FSGS
Classification of FSGS
FSGS arising from reduced nephron mass or glomerular adaptations to injurious insults.
Does not typically present with nephrotic syndrome
FSGS
Classification of FSGS
FSGS arising from reduced nephron mass or glomerular adaptations to injurious insults.
EM generally reveals <80% segmental foot process effacement of nonsclerotic glomeruli.
FSGS
Classification of FSGS
FSGS arising from focal proliferative GN or hereditary nephropathies such as Alport syndrome.
FSGS
Genetic Predisposition to FSGS
APOL1: located on chromosome 22, in linkage disequilibrium with MYH9, codes for apolipoprotein L-1
FSGS
Genetic Predisposition to FSGS
Missense mutations of APOL1 are thought to predispose patients of African descents (rather than MYH9 in earlier reports) to an excess risk of FSGS, HIVAN and chronic hypertensive nephrosclerosis. Greatest risk: mutation of 2 alleles.
FSGS
Genetic Predisposition to FSGS
The same APOL1 mutations are protective against Trypanosoma brucei, a parasite spread by tsetse flies in Africa.
FSGS
Etiologies of FSGS
Primary FSGS:
Presence of the soluble form of urokinase receptor (suPAR) was previously thought to be a candidate in the pathogenesis of primary FSGS. This has been largely disproved.
FSGS
Etiologies of FSGS
Primary FSGS:
Cardiotropin-like cytokine circulating factor has also been implicated in primary FSGS.
FSGS
Etiologies of FSGS
Primary FSGS:
Pathogenic circulating factor for primary FSGS remains unknown.
FSGS
Etiologies of FSGS
All other etiologies of FSGS:
Familial/genetic: mutations including nephrin (NPHS1), podocin (NPHS2), α-actinin 4, transient receptor potential cation 6 (TRPC6), WT1, informin-2, SCARB2 (LIMP2), formin (INF2), CD2-associated protein, mitochondrial cytopathies
FSGS
Etiologies of FSGS
All other etiologies of FSGS:
Virus: human immunodeficiency virus type-1, parvovirus B19, simian virus 40, CMV, Epstein–Barr virus