Abstract: An observational cohort with 40 patients (20 patients with primary FSGS and maladaptive FSGS, respectively) was carried out to identify renal morphometric parameters of interest. In addition, a validation cohort with 40 patients (20 patients with primary FSGS and maladaptive FSGS, respectively) was established to confirm the results matching age. estimated glomerular filtration rate (eGFR), and level of proteinuria. In the observational cohort, they found that the mean interglomerular area (MIA), a marker of glomerular scarcity described in the table 2) was significantly lower in patients with primary FSGS compared to maladaptive FSGS 90 [76-100] vs. 198 [165-299] ?m2. p<0.0001. This finding was confirmed in the validation cohort 133 [109-159] vs. 204 [170-339] ?m2 (p=0.0017).

Abstract: Inventors have shown that the protein isthmin-1 (ISM-1) is expressed at kidney level in animal and human model. They have also shown that this protein is expressed on the surface but also intracellular of the circulating leukocytes. They have observed that its expression is increased when a subject suffers from INS, MCN or FSGS compared to healthy controls. Among various causes of nephrotic syndrome, ISM-1 leucocyte expression is dramatically increased in patients with INS, MCN or FSGS. Accordingly, the present invention relates to a method for diagnosing INS, MCN or FSGS in a subject comprising the steps of: i) measuring the membrane expression level of isthmin-1 on the circulating leukocytes in a biological sample obtained from said subject; ii) comparing the expression level measured at step i) with its predetermined reference value, and iii) concluding that the subject suffers from INS, MCN or FSGS when the membrane expression level of isthmin-1 is higher than its predetermined reference value.