Proteomic analysis of plasma and urine samples performed on patients with recurrent FSGS post transplant identified a high-molecular-weight form of Apolipoprotein A-I, named as ApoA-Ib in 93% of recurrent FSGS urines compared with <5% of those without recurrence, patients with non- FSGS proteinuric diseases, or patients transplanted for familial FSGS. This evidence concerns the gene APOA1 and focal segmental glomerulosclerosis.