Table 1.

Causes of FSGS

Primary	Circulating podocyte-toxic factor
Secondary: Maladaptive	Reduced number of functioning nephrons (e.g., unilateral renal agenesis, renal dysplasia, oligomeganephronia, glycogen storage disease, low birth weight)
	Abnormal stress on an initially normal nephron population (e.g., morbid obesity, surgical reduction of renal mass [usually >75%], reflux nephropathy, high-protein diet, sickle cell disease, any advanced kidney disease with substantial loss of nephrons)
	Other causes: sleep apnea, cyanotic congenital heart disease, renal artery stenosis, malignant hypertension, cholesterol emboli
Secondary: Viral	HIV (established), CMV (probably), parvovirus B19 (possibly), EBV (possibly), HCV (possibly), hemophagocytic syndrome (possibly)
Secondary: Drug induced	Direct-acting antiviral therapy (ledipasvir, sofosbuvir), mTOR inhibitors, calcineurin inhibitors, anthracyclines, heroin(adulterants), lithium, IFN, anabolic steroids
Genetic	Renal limited (Table 2)
	Syndromic (Table 3)
Unknown

CMV, cytomegalovirus; EBV, Epstein-Barr virus; HCV, Hepatitis C virus; mTOR, mammalian target of rapamycin. IFN, interferon