Focal Segmental Glomerulosclerosis: A Morphologic Diagnosis in Evolution

Abstract

Abstract Context.—The diagnosis of focal segmental glomerulosclerosis (FSGS) is a descriptive pathologic diagnosis that in certain clinical situations (ie, primary or idiopathic) becomes its own disease. The clinical diversity, varied histology, and nonspecific morphologic features of FSGS all contribute to the complexity and problematic nature in making a pathologic diagnosis of FSGS. The definitions of the disease and of the morphologic features have evolved during the last century. Objective.—To review historic and morphologic features of FSGS in order to demonstrate a practical approach in achieving a pathologic diagnosis of FSGS on kidney tissue. Data Sources.—In 2004 a working proposal on the pathologic (morphologic) classification of FSGS was published in an attempt to unify the complexity of diagnosing FSGS, and it has shown to be both reproducible and with unique clinical implications for each defined FSGS variant. Conclusions.—An accurate diagnosis of FSGS can be challenging. During the last few decades, numerous new scientific discoveries have enriched our knowledge of pathogenetic mechanisms of nephrotic syndrome. Thus, it is expected there will be a need for a further modification to a morphologic classification and that the pathologist's role in diagnosing FSGS will remain in evolution. This review recapitulates the history of the pathologic diagnosis of FSGS and a current morphologic classification, hopefully opening up a discussion for further modifications that reflect the status of knowledge evolving in the 21st century.