Abstract
Background: Denys-Drash syndrome (DDS) is a very rare genetic disease. Wilms' tumor, genital abnormalities, and congenital glomerulopathy are the main features of DDS which resulted from a heterozygous mutation in the WT1 gene.
Case Presentation: First case of DDS has been diagnosed in Saudi Arabia in four months newborn who admitted to nephrology department with ambiguous bilateral undescended testis, and nephropathy. On admission, he had normal vital signs except high blood pressure. His kidney function tests showed abnormal kidney function. Ultrasonography and MRI were done to figure out his nephropathy and undescended testis, respectively. Both Abdominal ultrasonography and kidney histopathology confirmed diffuse mesangial sclerosis (DMS). MRI graph located the un-identical ectopic testis. The autosomal dominant inherited pathogenic missense mutation in exon 9 of WT1 gene (c.1181G>A (p.Arg394GLu)) was confirmed by DNA direct sequencing analysis. At his 4th year of age, his nephropathy developed to End Stage Renal Disease (ESRD).
Conclusion: DDS should be considered in new born baby with nephrotic syndrome and ambiguous gonads. DNA direct sequencing analysis for WT1 gene is very helpful for confirmation of DDS.

Key words: Denys-Drash Syndrome, DDS, WT1 gene, Wilm's tumor, nephropathy, diffuse mesangial sclerosis, DMS, undescended testis.