IntroductionSolitary median maxillary central incisor (SMMCI) syndrome is a rare and complex disorder that occurs in 1:50,000 live births. The developmental defects are mainly located in the craniofacial midline, namely: the midline cleft lip palate or congenital nasal malformation. Some of the associated anomalies belong to the holoprosencephaly (failure of the prosencephalon to laterise) spectrum but associated anomalies outside the holoprosencephaly spectrum have also been described. In most severe phenotypes the survival rate is low. Genetic and environmental factors acting between the 35th and 38th day of pregnancy are associated with the anomaly. The relationship of SMMCI to genes implicated in the pathogenesis of holoprosencephaly is still discussed controversially. A SHH missense mutation identified 2001 by Nanni et al. may be associated with SMMCI. SMMCI is characterized by a mostly symmetric central incisor of normal size, located exactly in the midline of the maxilla.Case reportA 9.5-year-old girl was presented at the Department of Orthodontics, Dentofacial Orthopedics and Pedodontics of Charité Berlin by her father, who was concerned about the single maxillary central incisor. The patient had a non-contributory history. A traumatic loss of one central incisor was ruled out, but a solitary median maxillary central incisor was present in the primary dentition, too. Clinical examination showed dolichofacial, symmetric face with mild hypotelorism, indistinct philtrum and hypoplastic nose. The most striking finding was the presence of a single central incisor that was located in the midline of the maxilla. Additional intraoral findings were the "V"-shaped high palate with an unusual prominent midpalatal ridge and the absence of labial frenulum and incisive papilla. The patient was also evaluated by a geneticist and no mutations of the SHH gene could be identified. According to the CBCT-findings, the midline maxillary suture was fused and therefore rapid maxillary expansion is not a treatment option for this patient. Extractions of the solitary median maxillary central incisor and of 2 mandibular incisors and sub sequent orthodontic space closure was the orthodontic approach followed for this patient.ConclusionFor the clinician it is important to assure an early detection of SMMCI syndrome with consideration of the patient’s needs in term of dental and medical care. Moreover, a multidisciplinary pedodontic, orthodontic and prothodontic treatment plan is necessary to ensure a successful dental treatment. Patients’ and parents’ perception, treatment needs and concerns should be evaluated carefully. In addition, SMMCI is considered one of the microforms of the holoprosencephaly spectrum and it can be associated with more severe anomalies or with a more severe phenotype of holoprosencephaly in the next generation. Therefore, we would like to underline the fundamental role of the dentist in the early diagnosis by identifying and referring these patients to the clinical geneticist for a further evaluation.