Nephrotic syndrome (NS) in the first year of life is uncommon and makes up a heterogeneous group of disorders. Subsequent studies have further defined the phenotype associated with mutations in the NPHS2 gene, revealing that patients usually develop NS from birth to 6 years of age. We report a child aged 4 months with steroid-resistant NS who had polymorphism of NPHS1 (E117K) and mutation of NPHS2 (P118L). Our patient was carrying a polymorphic NPHS1 mutation, while phenotypically she had a poor prognostic NPHS2 mutation. However, it must be questioned whether this polymorphic change (E117K) alters the signaling pathways of the podocytes and leads to P118L mutation, thus making it behave differently. Perhaps, this would be called a genetic modifier in future.