In steroid-resistant nephrotic syndrome (SRNS) Machuca et al. report that mutations of the recessive podocin gene cause adult-onset SRNS if the R229Q genetic variant occurs in a compound heterozygous state with another podocin mutation. Learning to tell apart the specific allele combinations of podocin mutations will be important for prognosis, genetic counseling in living related kidney donation, accurate etiologic classification within treatment studies, and the understanding of podocin function.