BACKGROUND: Differential diagnosis between primary focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) is sometimes difficult as nephrotic syndrome is the main clinical symptom in both diseases.OBJECTIVES: This study has attempted to evaluate the urinary excretion of Th1 and Th2 cytokines as potential biomarkers in distinguishing the two types of nephrotic syndrome, and predicting outcome of renal function.PATIENTS AND METHODS: Thirty-six patients with FSGS (M/F 22/14, Age; 41.9 ± 17 years, SCr=1.7 ± 0.8 mg/dL, UProt=4.7 ± 5.5 g/24 h), and 21 with MCD (M/F 5/16, Age; 41.4 ± 15 years, SCr = 1 ± 0.4 mg/dL, UProt = 7.9 ± 9.3 g/24 h) were included in the study. Τh1 (IL-2, IL-12, GM-CSF, INF-γ, TNF-α) and Th2 cytokines (IL-4, IL-5, IL-10, IL-13) were measured by multiple cytokine assay, Luminex technology, in first morning urinary samples collected at the day of renal biopsy.RESULTS: No significant differences in urinary excretion of all cytokines were found between FSGS and MCD patients. In FSGS however, IL-12 urinary levels were independent factor correlated with both global sclerosis (R = 0.5, = 0.009) and interstitial fibrosis (R = 0.5, = 0.02). Th1 cytokines (IL-2 and GM-CSF) were significantly increased in FSGS patients who did not respond to treatment ( = 0.03 and = 0.007, respectively). Th2 cytokines (IL-4, IL-5, IL-10, IL-13) were significantly increased in MCD patients with frequent relapses ( = 0.05, = 0.001, = 0.01, = 0.03).CONCLUSIONS: Urinary excretion of Th1 and Th2 cytokines cannot discriminate FSGS from MCD. Th1 cytokines, especially IL-12, IL-2 and GM-CSF, may be involved in pathology and progression of FSGS, while Th2 cytokines are implicated in frequent relapses of nephrotic syndrome in MCD.