[MIM 147 250]

(SICMMU, SMMCI)

Very rare: 1/50,000 births. A mutation of the SHH gene on 7q36, but also SIX3 on 2p21, ZIC2 on 13q32, TGIF on 18p11.3 or PTCH on 9q22.3 could be the cause. The presence of a single median central incisor is due to a lack of development of the median line of the craniofacial midface. Diagnosed around the age of 8 months, during the eruption of the first deciduous teeth, this dental anomaly is a warning sign, suggesting to search for other anomalies at the level of the median plane of the body as:

-         nasal malformation: atresia or choanal stenosis, congenital stenosis of the pear-shaped hole 

-         cleft lip and/or palate, or an aspect of median lip pseudocleft before the dental eruption

-         hypotelorism (45%), convergent squint

-         severe to moderate (50%) intellectual deficit 

-         microcephaly (33%)

-         abnormalities of the sella turcica and pituitary gland (10-50%); sometimes a panhypopituitarism (15%)

-         an underactive thyroid

-         atresia of esophagus or duodenum (10%)

-         vertebral anomalies in the neck (15%)

-         scoliosis

-         a heart malformation (25%): tetralogy of Fallot 

-         a renal malformation

-         a sexual ambiguity

There is a short stature linked to growth hormone deficiency in 50% of cases.

You can find this anomaly in case of (see these terms):

• holoprosencephaly
• CHARGE, VACTERL, velocardiofacial, ectodermal dysplasia, Duane syndrome, 47XXX
• deletion 18 p, deletion 7q36qter, deletion 22q11.2

Anesthetic implications: 

differential diagnosis of nasal obstruction in the newborn; according to the anomalies associated with.

References : 

• Hall RK. 
  Solitary Median Maxillary Central Incisor (SMMCI) syndrome. 
  Orphanet J Rare Diseases, 2006; doi: 10.1185/1750-1172-1-1-12
• Leraillez J. 
  L’obstruction nasale néonatale. 
  Arch Pédiatr 2001 ; 8 :214-20

Updated: March 2016