NPHP4 and Usher syndrome: Among the genes known to cause syndromic RP that were included in the gene panel used in our analysis, ALMS1, ARL6, BBS2, CLRN1, CNNM4, FLVCR1, HARS, MYO7A, NPHP4, OFD1, PANK2, PCDH15, TTC8, TTPA, USH1G, and USH2A and the genes causing Usher syndrome (CLRN1, MYO7A, PCDH15, and PDZD7; 1–9/100,000 globally [22–24]) and nephron phthisis (NPHP4; approximately 1/50,000 globally [25, 26]) are known to have a relatively higher prevalence among patients with syndromic RP.