A single maxillary central incisor (SMCI) may be a subtle but important phenotypic marker of an underlying genetic defect.
Synonym: solitary median maxillary central incisor (SMMCI)
Criteria: The presence of a single midline maxillary incisor, which affects both the decidual and permanent dentition.
SMCI may be present as a solitary finding, but usually is associated with other midline defects. The presence of multiple midline defects may be termed the SMMCI syndrome:
(1) microcephaly
(2) short stature
(3) hypopituitarism
(4) choanal atresia, pyriform aperture stenosis or other nasal malformations
(5) other dental anomalies
(6) cleft lip and palate
(7) congenital heart disease
(8) ocular anomalies
(9) other visceral anomalies
(10) intellectual disability
SMCI may be associated with holoprosencephaly (HPE). The gene mutations associated with HPE such as sonic hedgehog (SHH) and SIX3 should be looked for in affected patients.
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