Focal segmental glomerulosclerosis

Abstract

Focal and segmental glomerulosclerosis (FSGS) is a pattern of glomerular injury characterized by segmental sclerosis and/or hyalinosis involving some but not all the glomeruli. It is primarily a morphological diagnosis, and the term, FSGS, describes the characteristic distribution of the lesions in the affected glomeruli. It is emerging as the leading cause of nephrotic syndrome, not only in adults but, also in children, in many parts of the world. The lesion can occur in a wide variety of clinical settings and can occur in primary or secondary form. The subclassication of FSGS into primary and secondary forms is of utmost importance in determining optimal treatment and prognostication of the disorder. Primary FSGS, also known as idiopathic FSGS, is a clinicopathological syndrome characterized by heavy proteinuria and biopsy findings of FSGS, and there must be no evidence of an antecedent glomerulonephritis, a systemic disease with glomerular involvement or evidence of glomerular immune complex deposition. Secondary FSGS may result from diverse pathogenic mechanisms including heritable mutation of podocyte proteins, viral infections, toxins and medications. FSGS may also be mediated by adaptive structural/functional responses to diverse insults in the setting of reduced or normal nephron numbers. In this chapter, we will describe the nomenclature, classification, etiopathogenesis, morphology, clinical presentation and prognosis of the lesion. The discussion of treatment is beyond the scope of this chapter.