By using a multiplex PCR approach, Soliman et al. (2010) investigated the prevalence of the homozygous NPHP1 deletion among a cohort of 20 children from 17 independent Egyptian families who met the clinical and ultrasonographic criteria of nephronophthisis. Seventy-five percent of the studied patients were the products of consanguineous marriages, the percentage of affected siblings was strikingly high (65%, 13/20 patients), and 40% (8/20 patient) had a history of sibling death due to a similar condition. Soliman et al. (2010) reported that homozygous deletions in the NPHP1 gene were identified in six patients from five independent families of 17 families studied (29.4%), thereby confirming the diagnosis of type 1 (juvenile) nephronophthisis. Five patients had isolated nephronophthisis, whereas the sixth patient was among the Joubert syndrome-related disorders (JSRD) group, with distinct molar tooth sign detected on his brain MRI images, ataxia, retinitis pigmentosa, and dysmorphic facies. These findings led Soliman et al. (2010) to confirm that NPHP1 deletions can indeed be responsible for JSRD, as previously reported. Soliman et al. (2010) also documented the first report of a homozygous NPHP1 deletion in an infantile-onset nephronophthisis patient in whom the clinical manifestations began in the first year of life and progressed to End Stage Renal Disease (ESRD) by the age of 32 months. Soliman et al. (2010) concluded that the prevalence of homozygous deletions in the NPHP1 gene does not seem to differ in Egypt from that reported in Western countries.

Al-Romaih et al. (2011) studied two unrelated Saudi families with family histories of proteinuria, end stage renal disease, and various findings on kidney biopsy.  The diagnosis was initially thought to be focal segmental glomerulosclerosis (FSGS).  Sequencing analysis failed to identify the underlying genetic defects in nephrotic syndrome and FSGS genes.  Both families shared a region of homozygosity on chromosome 2q13 based on Whole-genome SNP analysis and homozygosity mapping.  Al-Romaih et al. (2012) identified a homozygous deletion of NPHP1 using polymerase chain reaction assay and exome sequencing.