Concordant nephrotic syndrome in twins with PAX2 and MYO1E mutations.

INTRODUCTION: The medical literature is scant with reports of twins diagnosed with nephrotic syndrome associated with genetic mutations. Mutations in the protein coding paired box gene 2 (PAX2) and in the non-muscle class I myosin, myosin 1E, (MYO1E) have been implicated in the development of steroid-resistant nephrotic syndrome. We describe the first case, to our knowledge, of the concordant presentation of nephrotic syndrome in twins with simultaneous mutations in PAX2 and MYO1E. CASE REPORT: At 32 months and 33 months of age, monochorionic, diamniotic twin girls presented with nephrotic syndrome. Each twin experienced three relapses during or after completion of corticosteroid treatment. Sustained remission was achieved with tacrolimus. Genetic testing of each twin revealed two heterozygous mutations of MYO1E and one homozygous mutation of PAX2. Renal biopsy results of one twin revealed pathologic findings consistent with minimal change nephropathy. The twins' phenotypes have been essentially identical. CONCLUSION: Our cases add to the scant medical literature addressing nephrotic syndrome in twins with genetic mutations. Close monitoring of our unique patients will provide novel information about the clinical significance of combined mutations in PAX2 and MYO1E.