A sibling from family GBB23 carries the homozygous pathogenic variant p.(Met390Arg) in BBS1, and additionally, the index case suffering from T2DM also carries the heterozygous variant p.(His3880Tyr) in ALMS1. Mutations in ALMS1 are the cause of Alström syndrome (ALMS; MIM #203800), an ultra-rare metabolic ciliopathy associated with severe visual impairment, sensorineural deafness, obesity, insulin resistance, T2DM, and hypogonadism, among other features42. This evidence concerns the gene BBS1 and obesity due to melanocortin 4 receptor deficiency.