KBG syndrome is a rare genetic disorder, characterized by short stature, moderate to severe degrees of mental retardation, developmental abnormalities of the limbs, bones of the spine (vertebrae), extremities, and/or underdevelopment of the bones of the skeleton. Abnormalities of the head and face (craniofacial dysmorphism) and malformations of the teeth and jaws (dento- skeletal dysplasia) may also be present. About 46 cases have been reported with KBG syndrome. The diagnosis is only based on clinical findings at age 7-8 years when the upper permanent central incisors erupt; the symptoms usually are not severe.

Some studies in families with KBG syndrome suggested that the disease shows an autosomal dominant pattern; while others suggested that it could follow an X-linked mode of inheritance in some cases. Researchers identified few heterozygous mutations in the ANKRD11 gene in KBG patients, suggesting that this gene is one of the causes of the disease. One of the mutations was G>C transversion at the splice acceptor site (7570-1G>C) in intron 10, resulting in the deletion of 2 residues located in the highly conserved C-terminal repression domain. Two de novo mutations have been identified in exon 9 in affected individuals with KBG, the first one was a 1-bp deletion (2305delT), while the second was a 2-bp deletion (5953delCA), causing a frameshift predicted to result in a premature termination codon.