[MIM 148 050]

(short stature-facial and skeletal anomalies-intellectual deficit-macrodontia syndrome)

Prevalence: unknown (< 1/106) but some atypical cases are probably undiagnosed. In about 50% of the cases, autosomal dominant transmission of a mutation of ANKRG11 gene (16q24.3): it is mainly the mother, often presenting a lighter clinical picture, who transmits the disease.

Association of 4 main points:

-        particular facial dysmorphism: round face (triangular in adolescence), thick eyebrows (sometimes moderate synophrys), hypertelorism, long philtrum, thin upper lip, broad nasal basis with anteverted nostrils  root,  wide  protruding ears;

-        macrodontia of permanent upper central incisors (85%), with sometimes a partial fusion of a central incisor  tooth with a lateral incisor one

-        skeletal abnormalities (mainly costovertebral): cervical rib, abnormalities of the vertebral arches leading to  spina bifida occulta at sacral or cervical level or scoliosis, pectus excavatum, hip dysplasia

-        developmental retardation: delay in walking, speech delay.

Are also observed in > 50% of cases:

-        harmonious short stature (66%),

-        EEG abnormalities, with or without seizures; brain abnormalities are sometimes associated: hypoplasia of vermis, type I Chiari malformation

-        low implanted hair on forehead and in the neck

Sometimes,

-        cutaneous syndactyly, brachydactyly (50%), clinodactyly

-        short webbed neck

-        cryptorchidism (31%),

-        hearing loss,

-        palateal anomalies (25%): cleft palate, bifid uvula, velar insufficiency with frequent otitis (44%)

-        strabismus

-        congenital cardiac anomalies: pulmonary artery stenosis, VSD, partial AVC

-        large anterior fontanel with late closure (22%)

-        autistic type behavior (24%) or hyperactivity disorders

Anesthetic implications:

check imaging of spine before making a neuraxial block; antiepileptic treatment; echocardiography

References : 

-         Brancati F, Sarkozy, A, Dallapiccola, B. 
KBG syndrome. 
Orphanet J Rare Diseases 2006; I: 50, doi: 10.1186/1750-1172-I-50

-        Low K, Ashraf T, Canham N, Clayton-Smith J, Deshpande C et al.
Clinical and genetic aspects of KBG syndrome.
Am J Med Gen Part A 2016 ; 170A :2835-46.

Updated: March 2017