R229Q polymorphism of NPHS2 gene in patients with late-onset steroid-resistance nephrotic syndrome: a preliminary study

Depending on the response to standard steroid therapy, nephrotic syndrome it is classified to steroid-sensitive and steroid-resistant nephrotic syndrome (SRNS). Mutations in several genes including NPHS2 have been implicated in SRNS. Gene R229Q polymorphism (p.R229Q) of NPHS2 is associated with adolescent- or adult-onset SRNS in European and South American populations. We investigated this polymorphism among a group of Iranian-Azeri patients with primary SRNS. All participants had the primary late-onset form of focal segmental glomerulosclerosis (FSGS) and their clinical feature was steroid unresponsiveness. They were compared with a group of age- and sex-matched individuals without any renal disease for NPHS2 gene as controls. The R229Q polymorphism (p.R229Q) was investigated in the case and control groups. A total of 25 patients (mean age, 26.6 +/- 8.0 years) with primary FSGS and 35 controls (mean age, 26.0 +/- 8.7 years) were studied. Serum creatinine of patients and their 24-hour protein excretion at the time of study were 2.4 +/- 1.94 mg/dL and 2830 +/- 981 mg/dL, respectively. Molecular study showed no p.R229Q polymorphism, neither in patients nor in controls. In this preliminary study, we showed that NPHS2 gene p.R229Q polymorphism does not present in Iranian-Azeri population with SRNS. Larger studies are needed to confirm our results and other mutated genes should also be considered in these patients.