Approach to differentiating primary, secondary, and genetic FSGS based upon clinical presentation and EM examination

FSGS: focal segmental glomerulosclerosis; EM: electron microscopy.
* An FSGS lesion is characterized by the presence of sclerosis in parts (segmental) of at least one glomerulus (focal) in the entire kidney biopsy specimen, when examined by light microscopy, immunofluorescence, or EM.
¶ Refer to relevant UpToDate content on the treatment of primary (idiopathic) FSGS.
Δ Commercial tests are available to detect mutations in over 50 FSGS genes. The most common methods of genetic testing for FSGS are direct (Sanger) sequencing and targeted sequencing by next-generation sequencing. Cost and availability may impact the clinician's ability to perform genetic testing. Refer to relevant UpToDate content on genetic causes of FSGS.