In our cohort, 4 possible triallelic cases have been identified, all of them diagnosed with BBS, 3 patients carrying biallelic BBS1 variants together with one allele in MKKS (MIM: 604896)9,12 and one additional case carrying biallelic MKKS variants and one allele in BBS5 (MIM: 603650). The gene discussed is BBS1; the disease is Bardet-Biedl syndrome.