Interestingly, germline mutations have been found in FAM111A in patients with Kenny–Caffey syndrome (KCS) and osteocraniostenosis (OCS)38–41, and it has been postulated that these mutations may cause gain-of-function FAM111A activity because the mutations are always heterozygous and no loss-of-function mutations (i.e., deletions and truncations) have been reported38. This evidence concerns the gene FAM111A and osteocraniostenosis.