The New Compound Heterozygous Mutation of NUP Nephropathy: Report of Two Cases and Literature Review

Abstract Backgrounds: NUP nephropathy is identified as a rare monogenic cause of steroid-resistant nephrotic syndrome recently. To explore the relationship between NUP mutation and renal disorders, we provide two cases and a literature review of the genotypical and phenotypical features in patients with NUP nephropathy.Results: We reported two patients with newly diagnosed NUP nephropathy who carried a compound heterozygous mutations in NUP107 and NUP93 gene respectively. Both patients were diagnosed steroid-resistant nephrotic syndrome and progressed to end-stage renal disease in childhood. While the mutation c.1537+1G>A in NUP93 gene was previously described, the mutations c.460A>G and c.1085C>T in NUP107 gene and c.1472A>T in NUP93 gene were novel. We also summarized the phenotypic and genetic spectrum of NUP nephropathy in eighty-six reported patients who carried 50 different mutations in 6 NUP genes (NUP107, NUP93, NUP205, NUP85, NUP133, NUP160). The majority of them were Asians (66/86, 76.7%). The mutation c.2492A>C and c.1079-1083del in NUP107 had been identified as the founder mutations in East Asian[1-3], while c.1772G>T and c.1886A>G in NUP93 might be the founder mutations in Western Europe and Turkish respectively. Nephrotic syndrome was the most common renal manifestation (68/86, 79.1%). Although the renal prognosis was poor that 80.8% (59/73) of them developed end-stage renal disease within the first two decades, the outcome of renal transplantation in NUP nephropathy is better than patients with other steroid-resistant nephrotic syndrome. Focal segmental glomerulosclerosis was the most prevalent renal biopsy pathologic type (56/65, 86.1%). Various extra-renal manifestations were found in 44.8% (26/58) of patients. Neurological involvement was the most common extra-renal presentation (22/26, 84.6%), including microcephaly (13/22, 59.1%), intellectual disability (12/22, 54.5%), and global developmental delay (10/22, 45.5%). Diverse abnormalities of the facial appearance (8/26, 30.8%), short stature (5/26, 19.2%),and contain convergent strabismus (4/26, 15.4%) had also been reported. There are significant differences in extra-renal manifestations between different genomics. Conclusions: The renal manifestation of NUP nephropathy is highly consistent that most patients suffered early-onset SRNS with FSGS. More than half of the patients had extra-renal symptom concomitantly. Asians showed potential susceptibility to NUP nephropathy. Despite the limited reports, some genotype-phenotype correlations have been gradually revealed.