Robin sequence (RS) can be defined as the combination of micrognathia and upper airway obstruction/glossoptosis causing neonatal respiratory problems, with or without a cleft palate and either isolated or non-isolated. Pathogenesis varies widely. We hypothesize that optimal treatment depends on pathogenesis and therefore patients should be stratified according to diagnosis. Here, we evaluate diagnoses and (presumed) pathogeneses in an RS cohort. Medical records of all RS patients presenting between 1995-2013 in three academic hospitals were evaluated. Four clinical geneticists re-evaluated all information, including initial diagnosis. Diagnoses were either confirmed, considered uncertain, or rejected. If uncertain or rejected, patients were re-evaluated. Subsequent results were re-discussed and a final conclusion was drawn. We included 191 RS patients. After re-evaluation and changing initial diagnoses in 48 of the 191 patients (25.1%), 37.7% of the cohort had isolated RS, 8.9% a chromosome anomaly, 29.3% a Mendelian disorder, and 24.1% no detectable cause. Twenty-two different Mendelian disorders were diagnosed, of which Stickler syndrome was most frequent. Stratification of diagnoses according to (presumed) pathogenic mechanism in 73 non-isolated patients with reliable diagnoses showed 43.9% to have a connective tissue dysplasia, 5.5% a neuromuscular disorder, 47.9% a multisystem disorder, and 2.7% an unknown mechanism. We diagnosed more non-isolated RS patients compared to other studies. Re-evaluation changed initial diagnosis in a quarter of patients. We suggest standardized re-evaluation of all RS patients. Despite the relatively high diagnostic yield pathogenesis could be determined in only 59.7% (71/119), due to limited insight in pathogenesis in diagnosed entities. Further studies into pathogenesis of entities causing RS are indicated.

The birth prevalence of Robin sequence (RS) is frequently cited to be 1 in 8,500 to 14,000 live births (range: 7,1-11,8 per 100.000), which is based on just a few epidemiological studies. The objective of this study is to contribute to the limited knowledge of the epidemiology of RS by determining the frequency of RS in a cleft palate (CP) population and the estimated birth prevalence in live births in the Netherlands, using distinct diagnostic criteria. A retrospective population-based analysis of the National Cleft Registry was performed in order to obtain all CP patients registered in the Netherlands from 2000-2010, in addition to a thorough review of the medical records in three Dutch Academic Pediatric Hospitals for the same period. Furthermore, a systematic search of the literature was conducted to allow for comparison of our findings. The Dutch birth prevalence of RS was estimated to be 1:5,600 live births (or 17.7 per 100,000), with a slight female predominance. RS was estimated to occur in a third of the CP population and patients with RS had a more severe cleft grade than the general CP population. The literature search yielded 42 studies reporting the birth prevalence for RS, which varied between 1:3,900 and 1:122,400 (0.8-32.0 per 100,000), with a mean prevalence of 1:24,500 (8.0 per 100,000). The birth prevalence of RS in the Netherlands was higher than reported for most other countries when similar diagnostic criteria were used, with a slight female predominance. A third of the general CP could be classified as RS.

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ObjectivesPartial tooth agenesis is frequently observed in Robin sequence. Tooth anomalies are increasingly considered as an extended phenotype of the cleft palate population. The study objective was to compare the prevalence and patterns of tooth agenesis in a group of patients with non-syndromic Robin sequence (ns-RS) and a group with non-syndromic cleft palate (ns-CP).Materials and methodsThe panoramic radiographs of 115 ns-RS and 191 ns-CP patients were assessed for agenesis of the permanent dentition (excluding third molars) and the patterns recorded using the Tooth Agenesis Code.ResultsPartial tooth agenesis was observed in 47.8% of ns-RS and 29.8% of ns-CP patients with a greater prevalence in the mandibula than in the maxilla, particularly in ns-RS. The teeth most frequently absent in both groups were the mandibular second premolars and maxillary lateral incisors. Tooth agenesis was bilateral in two-thirds of affected ns-RS patients and one-half of ns-CP patients. In ns-RS, bilateral agenesis of the mandibular second premolars was more frequently observed in female than that in male patients. Completely symmetrical patterns of hypodontia were found in around 45% of ns-RS patients with tooth agenesis compared to 35% in ns-CP. No association was found between the extent of the palatal cleft and the severity of hypodontia.ConclusionTooth agenesis is more prevalent in ns-RS than that in ns-CP, demonstrates a much greater predilection for the mandible in ns-RS, and bears no relation to the extent of the palatal cleft.Clinical relevanceWhen compared to ns-CP, additional developmental disturbances are likely involved in the etiology of tooth agenesis in ns-RS. Future research could help identify the underlying genetic traits and aid in classifying patients in those with and without expected tooth agenesis in order to facilitate orthodontic management strategies.