Silver-Russell syndrome: phenotype features and oral health status | Orphanet Journal of Rare Diseases

In the available literature, there are few reports presenting the characteristic oral phenotypic features observed in patients with Silver-Russell syndrome. These are usually descriptions of small groups of patients or single case reports. Authors typically focus on analyzing extraoral features characteristic of the syndrome and orthodontic diagnosis [5, 7, 8, 10, 15,16,17]. Among the few publications on the oral health status of patients with Silver-Russell syndrome, there is little information on the presence of characteristic intraoral phenotypic features and the intensity of caries, hygiene and gingival status in these patients. Knowing these is important both in the diagnostic process and in planning dental care, Vo Quang et al. [8] conducted a study to define the maxillofacial phenotype in patients with SRS. The study included 31 patients with SRS. Considering the rarity of the disease, this is a large group of subjects. The spectrum of facial dysmorphism is often incomplete in patients with SRS. However, new characteristics were demonstrated: small forehead, small mandible, skeletal class II, crowding of teeth in the lower arch and overbite. These observations are consistent with the results obtained in the above study.

According to reports by most researchers, patients with Silver-Russell Syndrome have a predisposition to the presence of narrowing of dental arches, crowding and Class II defects [2, 3, 8, 15], gothic palate and hypodontia involving premolar teeth, as well as micrognathia and microdontia [7, 10, 15, 18, 19] and disorders of tooth shape and size [2, 5, 8]. In the above study, we noted with a high frequency the presence of a gothic palate among patients with SRS. Marczak-Hałupka et al. [19], in a review paper describing the characteristics of patients with SRS, point to the presence of a high palate and hypodontia of premolar teeth as one of the main oral manifestations, which was also observed in the above study. The incidence of gothic palate in SRS patients is also confirmed by the studies of Jagielska et al. [20] and Cammarata-Scalisi et al. [21]. According to Cammarata-Scalisi et al. [21], gothic palate occurs in patients with hypomethylation in the 11p15.5 region.

In the present study, in addition to Class II defects, we also noted a trend toward deep or crossbite in patients with Silver-Russell Syndrome. Defects of this type have also been noted by other researchers [5, 22]. Wakeling et al. [1] emphasize that the upper dental arch is often narrow and crowded, and with coexisting facial asymmetry, a crossbite can occur, making it difficult for patients to chew properly. Despite the tendency toward a skeletal open bite in children with SRS, Bergman et al. [9] showed that as many as 31% of patients exhibited a deep bite, indicating compensatory alveolar growth. Facial asymmetry was assessed by body asymmetry, but no facial asymmetry of clinical significance was found. The prevalence of malocclusion was also higher in children with SRS, which may lead to an increased need for orthodontic treatment. Interestingly, Class II malocclusions were observed with a similar frequency to those of the control group. The possible correlation of crossbites with SRS is caused by uniparental disomy of chromosome 7 (UPD7). The literature reports that patients with UPD7 may represent distinct phenotypic entities of SRS, defined as a benign phenotype [23].

Reports of the occurrence of cleft palate in SRS patients have also been encountered in the literature [2, 15, 17], but we did not observe this abnormality frequently among the patients we studied (1 case out of 24 patients examined). Patients with cleft palate have been described by Khalid et al. [15] and Shiraishi et al. [17]. Genetic analysis of the patients was performed, and H19-DMR hypomethylation was shown at chromosome 11, but no methylation was found at chromosome 7 in these patients [17]. Cleft palate or cleft uvula was found to occur in 7% of patients with ICR1 hypomethylation and in no patients with UPD7 [3]. This is supported by a study by Wakeling et al. [2], which found cleft palate or uvula only in patients with 11p15.5 hypomethylation.

A feature observed only in SRS patients in the above study was a reduction in tongue size, occurring in 29.16% of children. However, there are no reports in the literature on this subject.

Also, anatomical abnormalities in both permanent and deciduous teeth were found among children with SRS. Narrowing of the incisal edges and the presence of a vertical fissure on the labial surface of the tooth were noted. Abnormalities of tooth shape and size in patients with SRS were also described by Eggermann et al. [24], Ribeiro et al. [25] and Reddy et al. [26]. More than half of our SRS patients had enamel defects (54.16%). Opacities, hypoplasia and a combination of defects were observed. Hypoplasia and hypomineralization of tooth enamel were found in both the deciduous and permanent dentition in about 50% of the children studied by Kotilainen et al. [27]. They also observed that the morphology of the occlusal surface of some permanent first molars was atypical.

The occlusal and developmental abnormalities of the dentition (abnormal morphological structure, impaired formation of protein structure and mineralization) observed in the study group may promote bacterial biofilm retention and increase the risk of dental caries and gingivitis. Accumulation of plaque may also be facilitated by impaired oral self-cleaning mechanisms. Wakeling et al. [1] report that muscular hypotonia is typical, especially in younger children with SRS. Among almost 30% of our patients with Silver-Russell syndrome, we observed hypotonia of the orbicularis oris muscle and a reduction in the size of the tongue, as well as a low amount of resting saliva with a foamy or stringy consistency (25% of children).

Caries intensity was higher in the study group, both in deciduous and permanent teeth. The risk of tooth decay was also reported by other authors [7, 26]. Przystupa et al. [7] emphasize that the susceptibility to dental caries of SRS patients is not insignificant for the development of the stomatognathic system. Patients with anatomical features that predispose to the development of dental caries and accompanying hygienic negligence on the part of caregivers lead to tooth loss due to caries already in the first years of a child’s life. Gingivitis was observed twice as often in children with Silver-Russell syndrome as in the control group. There is a lack of information in the literature regarding changes in periodontal tissues in this syndrome. Certainly, however, predisposing factors of plaque accumulation and mouth breathing promote gingivitis, and malocclusion promotes gingival recession.

Unfortunately, in the above paper, we did not analyze potential oral health risks that may be associated with feeding disorders present in SRS patients (e.g., feeding difficulties or the need for enteral feeding). We can describe this as a kind of limitation of our study. Nevertheless, it should be mentioned that these disorders may be a factor in developing oral conditions in this group of patients. Common feeding problems for children with SRS were poor appetite, fussiness, slow feeding, and problems associated with oral-motor dysfunction [28]. This can promote the risk of giving children foods they are more willing to accept, such as sweet foods or those with a mushy, lagging consistency. This is a factor in the development of caries. Avoidance of chewing also leads to weak development of dental arches, which can predispose to malocclusion. Another aspect is the frequent occurrence of gastroesophageal reflux. Chronic regurgitation of gastric acids in patients with gastroesophageal reflux may cause dental erosion.