What is focal segmental glomerulosclerosis?
Focal segmental glomerulosclerosis (FSGS) is a class of glomerular diseases defined by focal and segmental patterns of scar in the kidney glomeruli.
This disease spectrum includes primary, genetic, and secondary diseases. Primary FSGS is diagnosed in patients without a known cause.
There are a number of genetic mutations that disrupt the structure and function of the glomerular podocyte and slit diaphragm that manifest as FSGS. Secondary FSGS may arise from various kidney insults that lead to a common end point of glomerular damage.
These secondary insults include:
• Viral infection: HIV, parvovirus
• Drugs: heroin, pamidronate
• Postinflammatory conditions: autoimmune diseases
• Vascular issues: atheroembolic disease, hypertension, sickle cell disease
• Reflux nephropathy
The sclerosing type of C1q nephropathy may be grouped with primary or secondary FSGS with the distinguishing factor of C1q in the glomeruli revealed on kidney biopsy immunofluorescence staining and electron dense deposits with electron microscopy.
The etiology of C1q nephropathy is unknown. Obesity-related glomerulopathy is also often considered a secondary FSGS that manifests with glomerular hypertrophy in addition to the sclerosis of FSGS.
The common factor in these conditions is damage to the glomerular structure.
5 Interesting Facts
1. FSGS represents a spectrum of primary, genetic, and secondary diseases that manifest with characteristic glomerular scaring and proteinuria.
2. FSGS is more common in African Americans, mostly due to a high-risk APOL1 genotype in individuals of African ancestry.
3. Proteinuria is the common clinical laboratory manifestation of FSGS and may be accompanied by edema, reduced glomerular filtration rate, and hypertension.
4. Mutations in multiple genes that direct the structure and function of the podocyte and slit diaphragm have been implicated in familial and sporadic FSGS.
5. Primary FSGS recurs in 10% of initial kidney allografts and increases the risk for allograft failure.
