Nonsense pathogenic variants in exon 1 of PHOX2B lead to translational reinitiation in congenital central hypoventilation syndrome.

Pathogenic variants in PHOX2B lead to congenital central hypoventilation syndrome (CCHS), a rare disorder of the nervous system characterized by autonomic dysregulation and hypoventilation typically presenting in the neonatal period, although a milder late-onset (LO) presentation has been reported. More than 90% of cases are caused by polyalanine repeat mutations (PARMs) in the C-terminus of the protein; however non-polyalanine repeat mutations (NPARMs) have been reported. Most NPARMs are located in exon 3 of PHOX2B and result in a more severe clinical presentation including Hirschsprung disease (HSCR) and/or peripheral neuroblastic tumors (PNTs). A previously reported nonsense pathogenic variant in exon 1 of a patient with LO-CCHS and no HSCR or PNTs leads to translational reinitiation at a downstream AUG codon producing an N-terminally truncated protein. Here we report additional individuals with nonsense pathogenic variants in exon 1 of PHOX2B. In vitro analyses were used to determine if these and other reported nonsense variants in PHOX2B exon 1 produced N-terminally truncated proteins. We found that all tested nonsense variants in PHOX2B exon 1 produced a truncated protein of the same size. This truncated protein localized to the nucleus and transactivated a target promoter. These data suggest that nonsense pathogenic variants in the first exon of PHOX2B likely escape nonsense mediated decay (NMD) and produce N-terminally truncated proteins functionally distinct from those produced by the more common PARMs.

Neurofibromatosis of the larynx causing stridor and sleep apnea.

BACKGROUND: Neurofibromatosis type 1 can rarely present in the larynx. Patients typically do not present with complete obstructive symptoms, but partial obstruction and stridor. We review our health centers' case series of two patients, the first of whom presented with persistent sleep apnea post tonsillectomy and adenoidectomy, and the second who presented with noisy breathing. Additionally, we will review the literature on the management and treatment options for children with this rare clinical entity. METHODS: Retrospective case review. CASE REPORT & RESULTS: A two-year old male underwent a sleep endoscopy following persistent evidence of obstructive sleep apnea on polysomnography after initial tonsillectomy and adenoidectomy. Family elicited concerns about noisy breathing at night and an accompanying video documented stridor while sleeping during the monitored polysomnography. Flexible fiberoptic laryngoscopy in the operating room revealed what appeared to be a cystic mass along the right aryepiglottic fold causing deviation of the laryngeal introitus towards the contralateral side. Subsequent direct laryngoscopy and excisional biopsy revealed pathology results consistent with a plexiform neurofibroma. A six-month-old patient with stertor and stridor was found to have a laryngeal mass, subglottic stensosis, and progressive airway obstruction due to plexiform neurofirboma in the supraglottis, subglottis, and trachea. We present a series of two patients incidentally diagnosed with neurofibromatosis type 1 by way of a laryngeal neurofibroma and review the literature on management options. Both patients were found to have accompanying café au lait spots. Both patients required tracheostomy for airway management, and one was successfully decannulated. CONCLUSION: Laryngeal neurofibroma is a rare anomaly that can manifest with airway obstruction. Both patients presented here subsequently were noted to have café au lait spots on physical examination. The Otolaryngologist should be reminded of this anomaly when evaluating a child with evidence of a submucosal laryngeal mass. We present our series including that of a patient whose diagnosis was prompted by persistent sleep apnea following adenotonsillectomy tonsillectomy and a patient with airway obstruction and subglottic stenosis due to a neurofibroma. The treatment of choice is complete excision of the neurofibroma while maintaining functionality of the larynx. This can lead to successful decannulation.

Lung function over the first 3 years of life in children with congenital diaphragmatic hernia.

OBJECTIVES: Infants with congenital diaphragmatic hernia (CDH) have variable degrees of pulmonary hypoplasia at birth. Few reports of lung function over the first years of life exist in this group of children. HYPOTHESIS: Pulmonary function abnormalities correlate with severity of neonatal disease and intensity of neonatal therapies needed. We also hypothesized that longitudinal measurements of lung function over the usual period of rapid lung growth would lend some insight into how the lung remodels in CDH infants. METHODOLOGY: Ninety-eight infants with CDH between 11 days and 44 months of age underwent pulmonary function testing (PFT) on 1-5 occasions using the raised volume rapid thoracic compression technique. Demographic data were also collected. MAIN RESULTS: Forced expiratory flows were below normal. Total lung capacity was normal, but residual volume and functional residual capacity were elevated. Children requiring patch closure, ECMO, or pulmonary vasodilators generally had lower lung functions at follow up. Additionally, longer duration of mechanical ventilation correlated with worse lung function. CONCLUSIONS: Lung functions of survivors of CDH remain abnormal throughout the first 3 years of life. The degree of pulmonary function impairment correlated both with markers of the initial degree of pulmonary hypoplasia and the duration of mechanical ventilation. Understanding the relationship between the phenotypic presentation of CDH and the potential for subsequent lung growth could help refine both pre- and postnatal therapies to optimize lung growth in CDH infants.