Congress of the European Orthodontic Society edition:90 location:Warsaw date:18-22 June 2014
Solitary Median Maxillary Central Incisor (SMMCI) is a rare condition occurring in 1 of 50,000 live births. It is considered as the most subtle form of the holoprosencephaly (HPE) spectrum and has been shown to be genetically heterogeneous. Here we report on six patients with SMMCI showing a range of other phenotypic anomalies with different degrees of severity, varying from mild HPE signs to associated intellectual disability (ID), and with different genetic background. Using array Comparative Genomic Hybridization (aCGH) pathogenic Copy Number Variations (CNVs) were found in 3 of the 6 patients. Two patients carried a deletion at the 18p11 chromosomal region comprising the TGIF1 gene while the other patient had a deletion at 7q36, including the SHH gene.
In one patient, a mutation in the SIX3-gene was detected with whole exome sequencing, while in the two remaining cases all known HPE-genes were excluded using multiplex ligation-dependent probe amplification (MLPA) and sequencing, but so far remain unsolved. One of the two latter patients was an isolated SMMCI case without any other visible dentofacial anomalies, while the other showed associated clinical features deviating from the HPE-spectrum. All clinical phenotype data were related to the genotype results.