Segmental odontomaxillary dysplasia (ORPHA:67039)
A rare oral disease characterized by unilateral enlargement of the right or left maxillary alveolar bone and gingiva in the region distal to the canines towards the maxillary tuberosity. In the enlarged region, dental abnormalities such as missing teeth, abnormal spacing and delayed eruption occur.
Epidemiology
The term segmental odontomaxillary dysplasia (SOD) was introduced by Danforth et al. in 1990. More than 60 cases of SOD have been described. SOD is often diagnosed in childhood both in males and females, with a slight male predominance.
Clinical description
The 2022, 5th edition, of the World Health Organization (WHO) Classification of Head and Neck Tumours has added Segmental odontomaxillary dysplasia (SOD) within the group of fibro-osseous lesions. SOD is asymptomatic with onset in 1st-2nd decades that usually halts around puberty. Unilateral facial signs: nonprogressive or slowly progressive overgrowth or undergrowth of soft tissues and/or bones (typically centred on the posterior maxilla, and leading to facial asymmetry), dental anomalies (missing teeth or abnormal dentition), gingival hyperplasia or abnormal gingivae, commissural lip fissures, hypertrichosis, cutaneous hyperpigmentation and/or erythema, cutaneous depression, and lip hypopigmentation. The main clinical features include: 1) an alveolar process characterized by unilateral enlargement of the maxillary alveolar bone and gingiva. Buccal as well as palatal enlargement of the alveolar bone is observed, although it is more pronounced on the buccal side. 2) Dentition is marked by abnormal spacing between erupted primary/permanent molars and adjacent teeth. The first permanent molars are often distally displaced. A depression in the palate can appear in the molar region. The canines erupt normally. Malformations of the primary molars, absence of one or both premolars and delayed eruption of adjacent teeth are regular findings. 3) On radiograph, the bone appears dense and sclerotic with abnormal trabeculation. Decreased size of the maxillary sinus in the affected side is observed. Primary teeth are characterized by enlargement of pulps. 4) Histological findings reveal immature bone with irregular trabecular and basophilic cemental lines resulting from alternating bone resorption and bone formation. Sparse narrow spaces with only a few fat cells are observed. The gingiva shows slight fibrosis without pathological changes. Tubular defects in the coronal dentine are present. An irregular pulp/dentin interface is present. A deficient osteoblast layer and widespread external resorption is also observed. Sometimes homolateral, subtle, cutaneous manifestations (hypertrichosis, cutaneous hyperpigmentation and/or erythema, cutaneous depression) might be present.
Etiology
It is a non-hereditary, unilateral developmental disorder. Somatic mosaic variants in PIK3CA, or ACTB genes have been described.
Diagnostic methods
Diagnosis is suspected on clinical presentation.
Differential diagnosis
Differential diagnosis includes hemimaxillofacial dysplasia (HMD), regional odontodysplasia, fibrous dysplasia (causes enlargement of bone tissue, but in this case affected bone growth is out of proportion with that of unaffected bones, and tooth malformations and missing premolars are not characteristics of the disease), focal cemento-osseous dysplasia (occurring in adults with no gingival enlargement or absence of teeth), and hemifacial hyperplasia (unilateral facial enlargement and precocious eruption and enlarged teeth in the affected region but not report of premolars absence). In HMD, ipsilateral facial hypertrichosis is present in addition to the SOD symptoms. Some authors consider SOD and HMD to be different manifestations of the same syndrome. The incisors and canines of the permanent dentition are commonly involved and agenesis of premolars is not a typical feature.
Genetic counseling
It is a non-hereditary, unilateral developmental disorder.
Management and treatment
Multidisciplinary treatment of SOD should include long-term follow-up as it is important for guidance in the management of this disorder. Implants have been successful in one reported case.
Prognosis
Life-long treatment is expected.

                            Last update: 
                            November 2023


                            - Expert reviewer(s): 
                            Pr Agnès BLOCH-ZUPAN | ERN CRANIO*


                                * European Reference Network