What are the pathologic findings in Focal segmental glomerulosclerosis?
As noted by its descriptive name, Focal segmental glomerulosclerosis initially is characterized by sclerotic lesions restricted to a segment of a subset (focal) of the glomeruli. Electron microscopy may confirm these changes and show widespread foot process effacement.
There are some pathology clues that suggest the Focal segmental glomerulosclerosis is secondary rather than primary:
• Less diffuse foot process effacement
• Foot process width may be normal
• Glomeruli may be enlarged (glomerulomegaly)
However, pathology alone cannot distinguish between the three categories of FSGS: primary, genetic, or secondary. There are a few exceptions:
• Immunoglobulin A (IgA) nephropathy as a secondary cause of Focal segmental glomerulosclerosis has IgA deposits identifiable by immunofluorescence
• Obesity-related glomerulopathy and Focal segmental glomerulosclerosis secondary to cyanotic congenital heart disease often have enlarged glomeruli in addition to the typical glomerular fibrosis
As the disease progresses, involvement of more glomeruli and sclerosis of entire glomeruli may occur. Interstitial fibrosis with tubular atrophy is a frequent finding. No significant immunoglobulin deposits are found in cases of primary Focal segmental glomerulosclerosis, and their presence suggests an alternative etiology or, at low amounts, trapping of immunoglobulin that is not pathogenic.
