In addition to marked differences in the age of onset, patients homozygous for NPHP1 deletions can vary dramatically in their phenotype, from isolated nephronophthisis with progressive CKD to Senior–Løken syndrome (SLSN), Bardet–Biedl syndrome (BBS), and mild forms of JBTS (Table 2) [104,105,106]. Here, NPHP1 is linked to Bardet-Biedl syndrome.