Phenotypic variability in Joubert syndrome is partially explained by ciliary pathophysiology.

INTRODUCTION: Joubert syndrome (JS) arises from defects of primary cilia resulting in potential malformations of the brain, kidneys, eyes, liver, and limbs. Several of the 35+ genes associated with JS have recognized genotype/phenotype correlations, but most genes have not had enough reported individuals to draw meaningful conclusions. METHODS: A PubMed literature review identified 688 individuals with JS across 32 genes and 112 publications to bolster known genotype/phenotype relationships and identify new correlations. All included patients had the "molar tooth sign" and a confirmed genetic diagnosis. Individuals were categorized by age, ethnicity, sex and the presence of developmental disability/intellectual disability, hypotonia, abnormal eye movements, ataxia, visual impairment, renal impairment, polydactyly, and liver abnormalities. RESULTS: Most genes demonstrated unique phenotypic profiles. Grouping proteins based on physiologic interactions established stronger phenotypic relationships that reflect known ciliary pathophysiology. Age-stratified data demonstrated that end-organ disease is progressive in JS. Most genes demonstrated a significant skew towards having variants with either residual protein function or no residual protein function. CONCLUSION: This cohort demonstrates that clinically meaningful genotype/phenotype relationships exist within most JS-related genes and can be referenced to allow for more personalized clinical care.

Mutations in the endothelin receptor type A cause mandibulofacial dysostosis with alopecia.

The endothelin receptor type A (EDNRA) signaling pathway is essential for the establishment of mandibular identity during development of the first pharyngeal arch. We report four unrelated individuals with the syndrome mandibulofacial dysostosis with alopecia (MFDA) who have de novo missense variants in EDNRA. Three of the four individuals have the same substitution, p.Tyr129Phe. Tyr129 is known to determine the selective affinity of EDNRA for endothelin 1 (EDN1), its major physiological ligand, and the p.Tyr129Phe variant increases the affinity of the receptor for EDN3, its non-preferred ligand, by two orders of magnitude. The fourth individual has a somatic mosaic substitution, p.Glu303Lys, and was previously described as having Johnson-McMillin syndrome. The zygomatic arch of individuals with MFDA resembles that of mice in which EDNRA is ectopically activated in the maxillary prominence, resulting in a maxillary to mandibular transformation, suggesting that the p.Tyr129Phe variant causes an EDNRA gain of function in the developing upper jaw. Our in vitro and in vivo assays suggested complex, context-dependent effects of the EDNRA variants on downstream signaling. Our findings highlight the importance of finely tuned regulation of EDNRA signaling during human craniofacial development and suggest that modification of endothelin receptor-ligand specificity was a key step in the evolution of vertebrate jaws.

Clinical delineation of the PACS1-related syndrome--Report on 19 patients.

We report on 19 individuals with a recurrent de novo c.607C>T mutation in PACS1. This specific mutation gives rise to a recognizable intellectual disability syndrome. There is a distinctive facial appearance (19/19), characterized by full and arched eyebrows, hypertelorism with downslanting palpebral fissures, long eye lashes, ptosis, low set and simple ears, bulbous nasal tip, wide mouth with downturned corners and a thin upper lip with an unusual "wavy" profile, flat philtrum, and diastema of the teeth. Intellectual disability, ranging from mild to moderate, was present in all. Hypotonia is common in infancy (8/19). Seizures are frequent (12/19) and respond well to anticonvulsive medication. Structural malformations are common, including heart (10/19), brain (12/16), eye (10/19), kidney (3/19), and cryptorchidism (6/12 males). Feeding dysfunction is presenting in infancy with failure to thrive (5/19), gastroesophageal reflux (6/19), and gastrostomy tube placement (4/19). There is persistence of oral motor dysfunction. We provide suggestions for clinical work-up and management and hope that the present study will facilitate clinical recognition of further cases.

Ventricular noncompaction and absent thumbs in a newborn with tetrasomy 5q35.2-5q35.3: an association with Hunter-McAlpine syndrome?

We report on an infant with tetrasomy of 5q35.2-5q35.3, an interstitial triplication on one chromosome and normal complement on the other. The patient has some features of Hunter-McAlpine syndrome including intrauterine growth retardation (IUGR), almond-shaped eyes, epicanthal folds, and downturned mouth with thin vermillion of the upper lip. In addition, left ventricular noncompaction and absent thumbs were identified, which have never been described in Hunter-McAlpine syndrome. This chromosome abnormality is distinct from those previously reported. Within this region of tetrasomy is MSX2, a highly conserved homeobox containing gene. Increased copies of MSX2 have been previously associated with craniosynostosis. Our patient's only skeletal defect is absent thumbs, also potentially related to increased dosage of MSX2 which is important for limb formation. In addition, MSX2 is expressed in the developing heart and overexpression of this gene may disrupt the co-regulation of other cardiac genes in this region, namely CSX1.

Severe micrognathia: indications for EXIT-to-Airway.

The ex utero intrapartum treatment (EXIT) procedure has become an important management option in cases of fetal airway obstruction. Select cases of severe micrognathia may be candidates for EXIT-to-Airway due to high-risk of airway obstruction at birth. Here we present three successful EXIT-to-Airway procedures for the management of congenital micrognathia in its most severe manifestations. CASE 1: A 23-year-old G3P1011 with a pregnancy complicated by severe micorgnathia, jaw index <5th percentile, as well as polyhydramnios. At 36 weeks EXIT-to-Airway was performed utilizing a bronchoscopically positioned laryngeal mask airway (LMA) during 23 min of uteroplacental support followed by tracheostomy. CASE 2: A 26-year-old G4P0120 with a pregnancy complicated by severe micrognathia, jaw index <5th percentile, and an obstructed oropharynx associated with polyhydramnios. At 37 weeks EXIT-to-Airway was performed with placement of tracheostomy. CASE 3: A 36-year-old G6P3023 with fetal magnetic resonance imaging (MRI) revealing esophageal atresia, polyhydramnios, and severe micrognathia with a jaw index <5th percentile. At 35 weeks the patient underwent EXIT-to-Airway with formal tracheostomy during 35 min of uteroplacental bypass. In the most severe cases of fetal micrognathia, EXIT-to-Airway provides time to evaluate and secure the fetal airway prior to delivery. We propose indications for EXIT-to-Airway in micrognathia to include a jaw index <5%, with indirect evidence of aerodigestive tract obstruction such as polyhydramnios, glossoptosis or an absent stomach bubble.

Cost analysis of mandibular distraction versus tracheostomy in neonates with Pierre Robin sequence.

OBJECTIVE: To evaluate costs associated with surgical treatment for neonates with Pierre Robin sequence (PRS). STUDY DESIGN: Retrospective cohort study. SETTING: Cincinnati Children's Hospital Medical Center. SUBJECTS AND METHODS: With Institutional Review Board approval, we retrospectively studied neonates with PRS treated from 2001 to 2009 with either tracheostomy (Trach), mandibular distraction (MD), or Trach with subsequent MD (Trach+MD). Actual charges over a 3-year period associated with operative costs, hospital stay, imaging and sleep studies, clinic visits, and related emergency room visits were collected. Home tracheostomy care charges were estimated individually for each patient. Charges were compared using regression and appropriate statistical analyses. RESULTS: Forty-seven neonates were included in the study (MD, n = 26; Trach, n = 12; Trach+MD, n = 9). Trach group patients had 2.6-fold higher charges than the MD group despite no difference in length of hospital stay. This difference increased to 7.3-fold when including home trach care-related costs. Trach+MD group patients had longer hospital lengths of stay and higher operation room (OR) fees, but no increased total charges compared with the Trach only group. CONCLUSIONS: For patients with severe PRS, mandibular distraction provides significant cost savings over tracheostomy ($300,000 per patient over 3 years). Increased costs with tracheostomy come from greater hospital-related charges, more frequent airway procedures, a higher incidence of gastrostomy tube feeds, and home trach care costs. A careful examination of long-term outcomes will be critical as mandibular distraction continues to gain acceptance for treatment of PRS.

Cleidocranial dysplasia with severe parietal bone dysplasia: C-terminal RUNX2 mutations.

BACKGROUND: Cleidocranial dysplasia (CCD) is an autosomal-dominant skeletal dysplasia syndrome that is characterized by widely patent calvarial sutures, clavicular hypoplasia, supernumerary teeth, and short stature. CCD is caused by mutations in the transcription factor RUNX2, which is known to function as a major regulator of bone differentiation. Despite the characterization of 67 unique mutations in 97 individual cases, and the availability of animal models, no obvious genotype-phenotype correlation has emerged. METHODS: We describe 3 new cases that were ascertained on the basis of a severe calvarial phenotype, that were associated with 3 novel mutations in the C-terminal region of RUNX2 distal to the DNA-binding runt domain. In addition, a review of all previously described cases was undertaken in an effort to standardize mutation nomenclature, characterize the position of known mutations relative to the runt domain, and explore the hypothesis that C-terminal mutations that preserve the runt domain may lead to more-severe craniofacial phenotypes. RESULTS: Upon mutational analysis of RUNX2, we identified either frameshift or splice-site mutations that affect the C-terminal region of the resultant protein distal to the runt domain. CONCLUSIONS: In the context of previously described mutations, these cases suggest that C-terminal mutations that preserve the DNA-binding runt domain while disrupting the SMAD 1,2,3,5 binding domain and the nuclear matrix targeting signal may be responsible for the severe phenotype observed.