FSGS Subtypes and Genetics: Why Classification Still Falls Short
The medical understanding of focal segmental glomerulosclerosis, or FSGS, remains incomplete despite a long-standing four-category classification system. Clinicians currently categorize the disease into primary, secondary, genetic, and undetermined forms, but this framework often fails to capture the complexity of patient pathology. Experts Kirk Campbell and Howard Trachtman note that while we have identified over 60 genes linked to podocyte and basement membrane proteins, these markers do not always predict clinical outcomes or treatment responses.
Primary FSGS is frequently linked to a circulating permeability factor that increases albumin leakage into the urine. Meanwhile, secondary FSGS stems from external factors like infections or medications that strain the kidney's filtration barrier. Genetic forms involve specific mutations where variants like APOL1 serve as critical modifiers in patients of African ancestry. This existing system provides a general starting point, but it lacks the precision required for personalized medicine.
Treatment options have historically been limited, with clinicians often relying on immunosuppressive drugs or blood pressure medications originally designed for other conditions. The recent approval of sparsentan represents a change in this landscape. As a dual endothelin type A and angiotensin II type 1 receptor antagonist, it targets two distinct pathways involved in podocyte injury and fibrosis simultaneously. This development marks the first pharmacotherapy specifically designed for FSGS, reflecting a shift toward targeted molecular intervention.
Moving forward, the medical community continues to debate how these new therapies integrate with traditional standards of care. As providers look to match specific subtypes with precise treatments, the existing diagnostic classifications will likely need updates to reflect our deeper biological insights. Future clinical practice will depend on balancing these established models with emerging genomic and mechanistic data to better serve patients.