Central Hypoventilation Syndrome Research Articles

Obstructive Apneas in a Mouse Model of Congenital Central Hypoventilation Syndrome

Rationale: Congenital central hypoventilation syndrome (CCHS) is characterized by life-threatening sleep hypoventilation and is caused by PHOX2B gene mutations, most frequently the PHOX2B27Ala/+ mutation, with patients requiring lifelong ventilatory support. It is unclear whether obstructive apneas are part of the syndrome. Objectives: To determine if Phox2b27Ala/+ mice, which present the main symptoms of CCHS and die within hours after birth, also express obstructive apneas, and to investigate potential underlying mechanisms. Methods: Apneas were classified as central, obstructive, or mixed by using a novel system combining pneumotachography and laser detection of abdominal movement immediately after birth. Several respiratory nuclei involved in airway patency were examined by immunohistochemistry and electrophysiology in brainstem-spinal cord preparations. Measurements and Main Results: The median (interquartile range) of obstructive apnea frequency was 2.3 (1.5-3.3)/min in Phox2b27Ala/+ pups versus 0.6 (0.4-1.0)/min in wild types (P < 0.0001). Obstructive apnea duration was 2.7 seconds (2.3-3.9) in Phox2b27Ala/+ pups versus 1.7 seconds (1.1-1.9) in wild types (P < 0.0001). Central and mixed apneas presented similar significant differences. In Phox2b27Ala/+ preparations, the hypoglossal nucleus had fewer (P < 0.05) and smaller (P < 0.01) neurons, compared with wild-type preparations. Importantly, coordination of phrenic and hypoglossal motor activities was disrupted, as evidenced by the longer and variable delay of hypoglossal activity with respect to phrenic activity onset (P < 0.001). Conclusions: The Phox2b27Ala/+ mutation predisposed pups not only to hypoventilation and central apneas, but also to obstructive and mixed apneas, likely because of hypoglossal dysgenesis. These results thus demand attention toward obstructive events in infants with CCHS.

Annual Respiratory Evaluations in Congenital Central Hypoventilation Syndrome and Changes in Ventilatory Management.

Background: Annual in-hospital respiratory evaluations (AREs) during wakefulness and sleep are recommended to assess ventilatory requirements in patients with congenital central hypoventilation syndrome (CCHS) aged ≥2-3 years based on expert consensus. This study aimed to determine if AREs in patients with CCHS led to changes in ventilatory management. Methods: Retrospective review of patients with CCHS who underwent AREs with or without polysomnography between 2017 and 2019 was conducted. Clinical symptoms, results of AREs, and subsequent changes in ventilatory management were analyzed. Results: We identified 10 patients with CCHS aged 4-20 years. All patients required assisted ventilation (AV) only during sleep delivered by positive pressure ventilation via tracheostomy (n = 7) or diaphragm pacing (n = 3). In total, 7 (70%) patients had abnormal oxygenation and/or ventilation requiring changes in ventilator settings or duration of AV. Six patients required an increase in settings and/or duration of AV, and only 1 patient required a decrease in ventilator settings. Two patients had awake hypercapnia during a routine outpatient visit that improved following increase in ventilator settings and a period of continuous AV. One patient who was previously ventilator-dependent only during sleep was identified to require 16 h per day of AV. All patients (n = 3) who reported symptoms such as headache or oxygen desaturations during sleep required an increase in ventilator settings. Conclusion: We report a high prevalence of changes in AV management following an ARE. Our results demonstrate the importance of regular AREs in patients with CCHS to assess their ventilatory requirements and optimize AV.

Paired-like homeobox gene (PHOX2B) nonpolyalanine repeat expansion mutations (NPARMs): genotype–phenotype correlation in congenital central hypoventilation syndrome (CCHS)

PurposeCCHS is an extremely rare congenital disorder requiring artificial ventilation as life support. Typically caused by heterozygous polyalanine repeat expansion mutations (PARMs) in the PHOX2B gene, identification of a relationship between PARM length and phenotype severity has enabled anticipatory management. However, for patients with non-PARMs in PHOX2B (NPARMs, ~10% of CCHS patients), a genotype–phenotype correlation has not been established. This comprehensive report of PHOX2B NPARMs and associated phenotypes, aims at elucidating potential genotype–phenotype correlations that will guide anticipatory management. MethodsAn international collaboration (clinical, commercial, and research laboratories) was established to collect/share information on novel and previously published PHOX2B NPARM cases. Variants were categorized by type and gene location. Categorical data were analyzed with chi-square and Fisher’s exact test; further pairwise comparisons were made on significant results. ResultsThree hundred two individuals with PHOX2B NPARMs were identified, including 139 previously unreported cases. Findings demonstrate significant associations between key phenotypic manifestations of CCHS and variant type, location, and predicted effect on protein function. ConclusionThis study presents the largest cohort of PHOX2B NPARMs and associated phenotype data to date, enabling genotype–phenotype studies that will advance personalized, anticipatory management and help elucidate pathological mechanisms. Further characterization of PHOX2B NPARMs demands longitudinal clinical follow-up through international registries.

Chinese guideline for the diagnosis and treatment of childhood obstructive sleep apnea (2020).

Chinese guideline for the diagnosis and treatment of childhood obstructive sleep apnea (2020).

Ondine's Curse in Frontotemporal Dementia with Parkinsonism Linked to Chromosome 17 Caused by MAPT Variants.

"Ondine's curse" or central hypoventilation, induces an apparently spontaneous failure of automatic respiratory drive, henceforth necessitating a conscious effort to breathe and sleep induced hypoventilation. It is typically seen in congenital central hypoventilation syndrome, but may be acquired. To highlight Ondine's curse as part of frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) secondary to microtubule associated protein tau (MAPT) variants. We describe the clinical and neuropathological findings in two patients with fatal Ondine's curse associated with FTDP-17 and secondary to MAPT variants (FTDP-17t). We discuss neuroanatomical correlates. We review two prior reports of central hypoventilation associated with MAPT variants suggesting that Ondine's curse occurs uncommonly in FTDP-17t. Despite variants affecting different regions of MAPT and a degree of heterogeneity in pathological findings, the patients reviewed all experienced central hypoventilation during their disease course. Tauopathy should be considered in patients with adult-onset Ondine's curse.

Improvement of hypoventilation in Phox2b mutant mice modelling the congenital central hypoventilation syndrome by etonogestrel, a potent progestin. Perspectives for a possible potentiation by serotoninergic drugs

Congenital central hypoventilation syndrome (CCHS) is a life-threatening disorder characterized by hypoventilation during sleep and absence of the ventilatory response to CO2/H+. The disease-causing mutations are generally polyalanine repeat expansion mutations of PHOX2B. Knock-in mice bearing the 7-alanine expanded allele of PHOX2B (the most frequent mutation in patients) exhibit massive loss of retrotrapezoid nucleus neurons, lack CO2/H + chemosensitivity, and die within hours after birth. No pharmacological treatment is available. Clinical observations revealed a recovery of CO2/H+ chemosensitivity in two adult female patients with CCHS, both under desogestrel, a potent progestin used for contraceptive purpose. We previously showed that in mice, etonogestrel (ETO), the active metabolite of desogestrel, increased baseline respiratory frequency (fR) by a medullary action involving the serotoninergic (5-HT) systems. Accordingly, we hypothesized that ETO may stimulate fR on Phox2b mutant mice modelling CCHS and that 5-HT drugs would improve this respiratory effect of ETO. Experiments were made on ex vivo medullary-spinal cord preparations from conditional RTN Phox2b mutant (Egr2cre/+;Phox2b27Alaki) and OF1 WT newborn mice (P0-P2). fR was assessed by recording the 4th spinal ventral root. Effect of ETO on fR under normopH and metabolic acidosis (MA) conditions was evaluated in presence or not of 5-HT reuptake inhibitor. Without ETO, the increase in fR induced by MA observed in WT mice was absent in Egr2cre/+;Phox2b27Alaki mutant mice. ETO restored a respiratory response to MA in Egr2cre/+;Phox2b27Alaki mutant mice. In OF1 WT mice, when ETO was associated with 5-HT reuptake inhibitor, the increase in fR induced by MA was enhanced. Surprisingly, this potentiation was not retrieved in Egr2cre/+;Phox2b27Alaki mutant mice at concentrations used in OF1 WT. ETO was able to alleviate hypoventilation in Phox2b mutant mice modelling CCHS by a medullary action. Modulation of 5-HT systems may improve the respiratory effect of ETO in WT mice, but further studies are necessary to determine whether this increase of ETO effect by 5-HT extends to mutant mice.

Variable phenotypes in congenital central hypoventilation syndrome with PHOX2B nonpolyalanine repeat mutations.

Congenital central hypoventilation syndrome (CCHS) is a rare disorder affecting the autonomic nervous system that is caused by variants in the paired-like homeobox 2B (PHOX2B) gene. About 10% of patients with CCHS have nonpolyalanine repeat mutations (NPARM) that are associated with severe phenotypes requiring continuous assisted ventilation, Hirschsprung's disease, and increased neural crest tumor risk. However, some patients with NPARM have milder phenotypes. Our objective was to describe the phenotypes in patients with CCHS PHOX2B NPARM. Retrospective case series of patients with CCHS PHOX2B NPARM was conducted at 2 children's hospitals to evaluate their phenotypes. We identified 8 patients with CCHS PHOX2B NPARM aged 3-31 years. Seven patients were diagnosed in infancy and 1 patient at 2 years of age. All patients presented with respiratory depression in the first 2 months of life. Only 1 patient was identified with a severe phenotype requiring continuous assisted ventilation, Hirschsprung's disease, and a neural crest tumor, which was resected. Five patients required positive pressure ventilation via tracheostomy only during sleep and 2 patients required oxygen only during sleep. Four patients had Hirschsprung's disease and 1 patient had a cardiac pacemaker due to a bradyarrhythmia. None of the patients had echocardiographic abnormalities. Patients with CCHS PHOX2B NPARM can have variable phenotypes, emphasizing the importance of implementing a plan of care that is individualized for each patient. The type of NPARM and their respective location on the PHOX2B gene may play a critical role in the severity of phenotypes displayed by each patient. Kasi AS, Li H, Jurgensen TJ, Guglani L, Keens TG, Perez IA. Variable phenotypes in congenital central hypoventilation syndrome with PHOX2B nonpolyalanine repeat mutations. J Clin Sleep Med. 2021;17(10):2049-2055.

862 Volume-Assured Pressure Support improves outcomes in a patient with Congenital Central Hypoventilation Syndrome

IntroductionCongenital Central Hypoventilation Syndrome (CCHS) is a condition caused by a mutation of the PHOX2B gene and an incidence of 1 in 50,000 live births. Clinically the condition is characterized by autonomic nervous system dysfunction, the most prominent feature of which is the failure of respiratory homeostasis during sleep. In patients severely affected, life-long ventilatory support is required. This might start as early as the newborn period. Subsequent adjustments are required due to their growth and development. The role of Volume-Assured Pressure Support (VAPS) ventilation in treatment of CCHS was only described in a couple reports before.Report of case(s)A 17-year-old female patient born at term and diagnosed with CCHS at birth at our center with a PHOX2B mutation confirmed. Her daytime ventilatory support was weaned at age 18 months and the tracheostomy was removed at age 10 years old. She relocated to another state, was lost to follow-up, and returned this year for adjustments of her ventilator whose settings had not been adjusted for several years. She was on a Trilogy 100 ventilator, in pressure-controlled mode with settings of EPAP 5, IPAP 20, and a rate of 22/min without supplemental oxygen. Her measured weight is 69kg, body mass index (BMI) 27. The patient complained of difficulty breathing while on those settings and reported decreased desire to use the machine. The patient was empirically switched to VAPS due to titration availability limitations during the COVID-19 pandemic. Initial AVAPS settings were: EPAP 4–7, PS 3–12, breath rate 16/min, TV 350mL. Upon implementing the changes, the patient reported improved comfort and increased usage. Average minute ventilation decreased from 10.5 to 5.8 L/min, patient triggered breaths increased from 1.1% to 12.3%, average breaths per minute decreased from 22.0/min to 16.2/min, the average peak flow 31.8 to 26.2L/min, tidal volume decreased from 463 to 355mL.ConclusionAVAPS ventilation can be successfully used in managing patients with CCHS, and it might be superior to pressure-controlled mode in certain cases, improving patient comfort and compliance.Support (if any)Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM.

563 Effect of PHOX2B Genotype and Age on Heart Rate Variability in Pediatric Patients with Congenital Central Hypoventilation Syndrome

Abstract Introduction Congenital Central Hypoventilation Syndrome (CCHS) is a rare neurocristopathy causing a wide array of cardiac autonomic nervous system (ANS) abnormalities (abnormal heart rate (HR) regulation, decreased HR variability (HRV), prolonged sinus pauses). CCHS is caused by mutations throughout the PHOX2B gene. Different types and locations of PHOX2B mutations have been associated with different levels of CCHS cardiac phenotype severity. We hypothesized that HRV in CCHS will be influenced by age and PHOX2B genotype. Methods PHOX2B mutation-confirmed CCHS patients in our cohort followed longitudinally with serial Holter monitoring were included. HRV measures were extracted from Holter monitoring reports and analyzed using linear mixed-effect models. Additional analyses explored which variables predicted sinus pauses and cardiac pacemaker implantation using linear and logistic regression. Only data preceding implantation of a cardiac pacemaker were included in analysis. Results 97 patients (0–18 years old) were enrolled in the study: 21 with the 20/25 genotype, 21 with the 20/26 genotype, 26 with the 20/27 genotype, 7 with genotypes ranging from 20/28-20/33, and 22 with non-polyalanine repeat expansion mutations (NPARMs). There were 965 total observations (Holters). The following HRV metrics were analyzed: min- and max-HR, longest-RR, SDNN, ASDNN5, SDANN5, and RMSDD. Statistically significant differences were observed between PHOX2B genotypes for min-HR and longest-RR (ps&amp;lt;0.05). Age by genotype interactions emerged such that certain metrics in HRV had different developmental trajectories by genotype (ps&amp;lt;0.05). Min-HR and longest-RR predicted eventual cardiac pacemaker implantation (AUCs&amp;gt;0.78). As for predictors of sinus pauses, different HRV metrics emerged as predictors across PHOX2B genotypes suggesting their utility in predicting cardiac pacemaker implantation dependent on genotype. Conclusion HRV in patients with CCHS is dependent on age and PHOX2B genotype, with significant differences in HRV metrics between patients with PHOX2B genotypes 20/25, 20/26, and 20/27 and the patients with 20/28-20/33 genotypes as well as those with NPARMs. Consistent with treatment guidelines, min-HR and longest-RR were predictive of eventual cardiac pacemaker implantation. Differences in the HRV metrics which predict sinus pauses as well as the overall group differences observed and trajectory-based differences may improve anticipatory management by earlier risk identification for prolonged sinus pauses in CCHS. Support (if any) None

821 An Unusual Pediatric PAP Compliance Obstacle, Even When the Mask Fits

Abstract Introduction Proper mask fitting is an important factor for compliant and effective use of PAP therapy. However, we present 2 patients whose masks became a barrier to PAP therapy despite a well-fitting mask. Report of case(s) Case 1 A 12-year-old female with ADHD, Chiari I malformation status-post decompression, and persistent mixed central and obstructive sleep apnea is managed with BPAP S/T. Despite absence of upper airway structural abnormalities, she is a mouth-breather during sleep and only tolerates full face masks. Despite ensuring a good mask fit and optimal BPAP settings to control her AHI, she sleeps with her neck hyperextended, resulting in her lower jaw pushing caudally and the mask liner slipping into her mouth. This stimulated chewing and resulted in damage to several masks. Case 2 An 8-year-old male with congenital central hypoventilation syndrome is managed with BPAP S/T during sleep. Similar to case 1, he is a mouth-breather during sleep and can only tolerate full face masks. Although his mask and headgear fit him well, he drools in sleep which results in the silicone liner slipping into his mouth, stimulating chewing. This has led to the need for replacement of several masks. Of note, drooling did not occur when he was previously using assisted ventilation via tracheostomy, and bruxism was not identified during polysomnography. Conclusion To our knowledge, this is the first report of PAP mask chewing, thus its incidence is unknown. We suspect that the mask liner slipping into the mouth touches the anterior surfaces of the teeth stimulating the chewing reflex. The frequency of mask chewing and consequent damage is unpredictable and often necessitates mask replacement. Insurance companies should consider this unique mask complication when determining their mask coverage policies since the typical 6-months interval for authorization of a new mask can impair the patient’s health, PAP compliance, and become an out-of-pocket financial burden for families. Although it did not occur in our patients, mask chewing may pose a potential choking hazard. Awareness of mask chewing may help in improving pediatric PAP mask development to ensure masks are safe. Support (if any):

848 Refractory Hypoventilation in Congenital Central Hypoventilation Syndrome: A Case for Average Volume-Assured Pressure Support

Abstract Introduction Congenital Central Hypoventilation Syndrome (CCHS) is a rare cause of alveolar hypoventilation in children resulting in lifelong ventilatory support. In older children requiring nocturnal support alone, the use of diaphragmatic pacing in conjunction with or independent of non-invasive ventilatory (NIV) support has been demonstrated to improve quality of life. We present a case of refractory hypoventilation despite escalation of NIV. Report of case(s) 20-year-old female with Hirschsprung’s disease and CCHS (20/26 polyalanine repeats) with history of invasive ventilation via tracheostomy who underwent bilateral diaphragmatic phrenic nerve stimulator placement at 13 years-of-age with subsequent tracheostomy decannulation. Diaphragmatic pacing was discontinued three years later in the setting of pneumonia and patient discomfort because of receiver positioning. At that time, she had improved subjective sleep quality and adequate ventilatory support on bi-level positive airway pressure (PAP) despite discontinuation of diaphragmatic pacing. Titration of bi-level PAP was done via polysomnogram four years later demonstrating nocturnal hypoventilation with transcutaneous CO2 values greater than 50 mmHg for 80% of the study and an oxygen nadir of 87% despite titration of inspiratory pressure and respiratory rate to maximize ventilatory assistance. The patient was subsequently admitted to the intensive care unit for transition to non-invasive average volume-assured pressure support (AVAPS) mode. Ventilation improved with nocturnal pCO2 values via capillary blood gas of 31 mmHg and 45 mmHg at 2 am and 6 am respectively. The patient was discharged on AVAPS therapy while undergoing evaluation to resume diaphragmatic pacing via cervical phrenic nerve stimulators for improved comfort. Conclusion Several ventilatory strategies may be employed in the care of patients with CCHS, with individualization of support based on phenotype, comorbidities, and patient and family preference. This case highlights the unique challenges of adequately ventilating patients as they age. The use of NIV via an AVAPS mode in patients with CCHS has been infrequently reported in the literature, though is promising in reported efficacy with regards to ensured ventilation. This, in conjunction with diaphragmatic pacing, may allow patients to achieve appropriate ventilation while maintaining quality of life, and could be considered in patients with refractory hypoventilation despite other modes of NIV. Support (if any):

The Role of Noradrenergic and Glutamatergic Signaling in Noradrenergic Neurons in Respiratory Control

Central noradrenergic (NA) neurons are a critical component of the brainstem respiratory network that maintains blood CO2 and O2 levels through respiratory chemoreflexes. NA dysfunction is implicated in numerous developmental respiratory disorders such as the fatal Sudden Infant Death Syndrome (SIDS), Rett Syndrome, and Congenital Central Hypoventilation Syndrome (CCHS), in which abnormal chemosensory function is implicated. However, which NA neurons modulate respiratory chemoreflexes and the underlying mechanisms are still not fully understood. Previous studies in our lab utilizing intersectional chemogenetic (hM4D and hM3D DREADD mediated) inhibition and excitation identified multiple rhombomere (transient genetically-defined hindbrain segments arising during early development) specific NA populations that play a role in the adult hypercapnic chemoreflex. NA neurons are typically thought to communicate with synaptic partners through noradrenaline as their primary neurotransmitter. However, the excitatory neurotransmitter, glutamate, is also expressed in subpopulations of NA neurons including those derived from rhombomeres playing a role in the hypercapnic reflex. Prior studies have implicated NA derived glutamatergic signaling in respiratory control. Thus, we seek to determine the relative roles of noradrenergic and glutamatergic signaling in rhombomeric NA populations that are involved in adult respiratory chemoreflexes. To determine the requirement of noradrenergic signaling in the hypercapnic reflex, we aim to conditionally ablate noradrenergic signaling in rhombomeric NA sub-populations by crossing rhombomere specific Credrivers with the THflox/flox(tyrosine hydroxylase) allele to remove dopamine and downstream (nor) adrenaline production in targeted neurons. We also aim to determine if the glutamate producing NA neurons represented a larger functional cohort in breathing control. We therefore used our intersectional strategy to target and chemogenetically activate (hM3D) or inhibite (hM4De) glutamate co-expressing NA neurons (defined by partially overlapping Vglut2Cre; DBHFLPo activity) which are expected to comprise a super-set of rhombomere specific NA neurons that play a role in respiratory chemoreflexes. Whole-body barometric plethysmography was used to measure the respiratory function of the mice under room air (21%O2,79%N2) and hypercapnia (21%O2, 74%N2, 5% CO2). Our preliminary data suggests that removing noradrenergic signaling in a key rhombomeric NA subpopulation does not inhibit the hypercapnic reflex while DREADD mediated inhibition does reduce the hypercapnic reflex. Acute inhibition of glutamate-expressing NA neurons shows a reduction in the hypercapnic ventilatory reflex while acute activation of these same neurons shows a significantly enhanced reflex. Altogether, these preliminary data suggest that glutamate production may delineate a functionally specific NA subpopulation in the hypercapnic reflex and offers additional clues to the respective roles of noradrenaline and glutamatergic signaling in the noradrenergic system.

Mice That Express a KCNQ2 Channel Gain‐of‐Function Variant (R201C) Exhibit a Blunted Ventilatory Response to CO 2

The KCNQ1-5 (Kv7)family of voltage gated K+ channels activate at subthreshold voltages and are important determinants of resting membrane potential. In particular, both loss- and gain-of-function KCNQ2 pathogenic variants are associated with neurodevelopmental disorders characterized by seizures, myoclonus, disordered breathing and early mortality. To understand how KCNQ2 channels regulate breathing and contribute to mortality, we developed a conditional mouse line that expresses a KCNQ2 gain-of-function mutation (R201C) that in humans causes severe respiratory problems reminiscent of congenital central hypoventilation syndrome (CCHS). Considering CCHS involves disruption of neurons in the retrotrapezoid nucleus (RTN) that regulate breathing in response to changes in CO2/H+ (i.e., function as respiratory chemoreceptors), we first used fluorescent in situ hybridization to confirm that Kcnq2 channels are expressed by chemosensitive RTN neurons identified based on location and expression of Phox2b. Next, we used whole-body plethysmography to characterize baseline breathing and the ventilatory response to CO2 or low O2 in control (N=6) and Phox2bcre::Kcnq2R201C/+ (N=4) mice (P30; mixed sex). We found that Phox2bcre::Kcnq2R201C/+ mice show diminished ventilatory response to graded increases in CO2. In 7% CO2 (balance O2), Phox2bcre::Kcnq2R201C/+ mice show noticeably reduced respiratory frequency (283.9 ± 26.8 bpm for Phox2bcre::Kcnq2R201C/+ compared to 359.5 ± 16.86 bpm for controls); tidal volume (0.024 ± 0.005 ml/g for Phox2bcre::Kcnq2R201C/+ compared to 0.031 ± 0.003 ml/g for control), and minute ventilation (6.9 ± 1.97 ml/min/g for Phox2bcre::Kcnq2R201C/+ compared to 11.08 ± 1.58 ml/min/g for control). Interestingly, Phox2bcre::Kcnq2R201C/+ mice also show an augmented ventilatory response to hypoxia compared to control mice. In 10% O2 (5 min exposure), Phox2bcre::Kcnq2R201C/+ mice show increased respiratory frequency (Phox2bcre::Kcnq2R201C/+ 268.5 ± 5.073 bpm compared to 223.4 ± 15.84 bpm for controls); tidal volume (0.014 ± 0.001 ml/g for Phox2bcre::Kcnq2R201C/+ compared to control 0.013 ± 0.001 ml/g), and minute ventilation (3.81 ± 0.361 ml/min/g for Phox2bcre::Kcnq2R201C/+ compared to 2.95 ± 0.235 ml/min/g for control). These results suggest mice expressing the KCNQ2 variant R201C in Phox2b expressing neurons recapitulate the hypoventilatory phenotype exhibited by patients caring this variant. Our results also suggest peripheral chemoreceptor drive partially compensates for diminished central drive in Phox2bcre::Kcnq2R201C/+ mice.

Generation and characterization of iPSC lines (BCH001) from a boy with intron 14 mutation in the ret proto-oncogene (RET) gene

Congenital central hypoventilation syndrome (CCHS) is characterized by an alteration of the ventilatory response to hypercapnia and hypoxia, and is classically presented in neonates with abnormalities of the autonomic nervous system. Here, we generated human induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells (PBMCs) isolated from a male patient clinically diagnosed with CCHS. These iPSC lines carry a heterozygous RET mutation (c.2608-125C > T), express pluripotency markers, have the capacity to differentiate into the normal teratoma tissue, retain the RET mutation and display the normal karyotype, which will also provide a useful resource to study the pathogenesis of CCHS.

Tracheostomy decannulation to noninvasive positive pressure ventilation in congenital central hypoventilation syndrome.

Noninvasive positive pressure ventilation (NPPV) may permit tracheostomy decannulation (TD) in patients with congenital central hypoventilation syndrome (CCHS) requiring nocturnal positive pressure ventilation via tracheostomy (PPV-T). There is limited evidence on optimal strategies for transitioning patients from PPV-T to NPPV. This study aimed to describe the clinical course and outcome of children with CCHS who underwent TD and transitioned from PPV-T to NPPV. Retrospective review was conducted on patients with CCHS using nocturnal PPV-T who underwent TD to NPPV. The results of clinical evaluations, airway endoscopy, polysomnography, and clinical course leading to TD were analyzed. We identified 3 patients with CCHS aged 8-17 years who required PPV-T only during sleep. Patients underwent systematic multidisciplinary evaluations with a pediatric psychologist, pulmonologist, sleep physician, and otolaryngologist utilizing a TD algorithm. These included evaluation in the sleep clinic, NPPV mask fitting and desensitization, endoscopic airway evaluation, daytime tracheostomy capping, acclimatization to low-pressure NPPV, polysomnography with capped tracheostomy and NPPV titration, and if successful, TD. All patients underwent successful TD following optimal titration of NPPV during polysomnography. The duration to TD from decision to pursue NPPV was between 2.4 and10.6 months, and the duration of hospitalization for TD was between 4 and 5 days. There were no NPPV-related complications; however, all patients required surgical closure of tracheocutaneous fistula. NPPV may be an effective and feasible option for patients with CCHS requiring PPV-T during sleep and permits TD. In patients with CCHS, a systematic multidisciplinary algorithm may optimize successful transition to NPPV and TD.

Genetic mutation in Hirschsprungs/congenital central hypoventilation syndrome

Abstract Background Congenital central hypoventilation syndrome (CCHS) is a disorder of respiratory and autonomic regulation which presents with hypoventilation. In some patients, CCHS is associated with Hirschsprung disease and as such known as Haddad syndrome. Case presentation A preterm was referred to our intensive care unit due to suspicion of meconium ileus after loop-ileostomy at the age of 8 days. The patient presented with recurrent apnea, did not respond to caffeine citrate, and was dependent on ventilation. Furthermore, the patient was unable to pass stool spontaneously. In the course of clinical deterioration, fluoroscopy showed a perforation next to the ileostomy and resection of ileum was conducted. An ileostomy was performed, and several biopsies of the intestines were taken. Neither in the biopsies nor in the resected segment were ganglion cells identified histopathologically. Considering the poor prognosis, life support was withdrawn. Autopsy and histology verified total aganglionosis of the intestines. Genetic testing confirmed a rare pathogenic deletion in the alanine-repeat region in the PHOX2B (c.722-759del; p.Ala241Glyfs*106). Conclusion CCHS and intestinal aganglionosis are hints for Haddad syndrome. To confirm the diagnosis, biopsies of the intestines and genetic testing for mutations in the PHOX2B gene should be performed.

Congenital central hypoventilation syndrome in neonates: report of fourteen new cases and a review of the literature.

BackgroundCongenital central hypoventilation syndrome (CCHS) is a rare autosomal dominant disorder caused by pathogenic variants in paired-like homeobox 2B (PHOX2B) gene. Characteristics of neonatal-onset CCHS cases have not been well assessed. The aim of this study is to expand current knowledge of clinical and genetic features of neonates with CCHS and provide data on the genotype-phenotype correlation.MethodsWe made a retrospective analysis of 14 neonates carrying PHOX2B pathogenic variants from 2014 to 2019 and we reviewed previously published neonatal-onset cases. Clinical and genetic data were analyzed. Moreover, genotype-phenotype correlation analysis was performed.ResultsWe identified a total of 60 neonatal-onset CCHS cases (35 males and 25 females) including 14 novel cases from our local cohort. Nearly 20% (18.2%) of the patients were born prematurely. Nearly half (46.2%) of the patients had abnormal family history. Polyhydramnios was observed in 21.3% (10/47) of the patients. About 90% of the patients manifested symptoms of hypoventilation in the first week of life. Fourteen patients (23.3%) were classified as mild-CCHS and the rest were severe-CCHS. Gastrointestinal manifestations were observed in 71.7% of the patients. Approximately twofold more males than females were affected by Hirschprung disease (HSCR)/variant HSCR (75.8% vs. 35%, P=0.003). Neural crest tumor occurred in 9.1% (4/44) patients. Half patients had polyalanine repeat expansion mutations (PARMs) in PHOX2B (seven with 25 PARM, nine with 26 PARM, twelve with 27 PARM, one with 28 PARM and one with 31 PARM) and the other half patients had 23 distinct non-polyalanine repeat expansion mutations (NPARMs) with one novel pathogenic variant (c.684dup). The prevalence of HSCR and mild-CCHS among patients with NPARMs was significantly greater than that of the patients with PARMs.ConclusionsThis report provides a large cohort of neonatal-onset CCHS cases. The results indicate that severe hypoventilation and HSCR are frequently observed in this group. NPARMs accounted for half of the cohort with some genotypes tend to be associated with mild phenotype. Molecular testing in neonates with suspicion of CCHS and genetic counseling for CCHS families are highly recommended.

Targeted Hot Spot Sequencing of Uzbek Lung Cancer Patients

Objectives: Carcinoma of lung is a widespread multifactorial disease with a poor prognosis. Uzbek lung cancer patients screening for prevalent mutations, associated with cancer development by targeted next generation sequencing was the main objective of current research. Materials and methods: Preparation of sequencing libraries was conducted using the Illumina Cancer Hot spot Panel v2 covering mutational hot spot regions of 50 cancer genes, from DNA extracted from formalin-fixed paraffin-embedded tumor samples of 10 patients. Sequencing was performed with the Mi Seq Next Generation Sequencing machine(NGS). Results: Hot spot mutations data analysis revealed clinically benign mutations in allstudied samples, with 70% having 3 or more mutations stored in the COSMIC database.According to ClinVarFGFR3 gene was associated with Crouzon syndrome with acanthosis nigricans, PDGFRA, EGFR and TP53 gene mutations were corellated with Idiopathic hypereosinophilic syndrome, Lung cancer and Glioma susceptibility respectively.KIT and KDR gene mutations were, respectively, associated with Gastrointestinal stromal tumor and Hemangioma, capillary infantile. Synonymous variants in RET and HRAS genes, were associated congenital central hypoventilation and epidermal nevus syndrome respectively. EGFR gene mutations occurred exclusively in patients with adenocarcinoma G2. where as MET and BRAF mutations were identified in bronchioalveolar cancer samples. Conclusion. In conclusion, particular polymorphisms and mutations affect treatment response and the toxicity level among patients with lung cancer, undergoing chemotherapy. Variety of SNPs were reported to have impact on disease outcomes of those patients, therefore they should be validated in an independent population, prior to being adopted for pre-personalised therapy screening.

How the Management of Children With Congenital Central Hypoventilation Syndrome Has Changed Over Time: Two Decades of Experience From an Italian Center.

Background: Congenital central hypoventilation syndrome (CCHS) is a rare disorder whose clinical phenotype is closely related to genotype.Methods: A retrospective analysis has been conducted on 22 patients with CCHS, who were referred to the Pediatric Pulmonology and Respiratory Intermediate Care Unit of Bambino Gesù Children's Hospital (Italy) for a multidisciplinary follow-up program between 2000 and 2020.Results: Apnea and cyanosis were the most frequent symptoms at onset (91%). Overall, 59% of patients required tracheostomy and invasive mechanical ventilation (IMV) in the first months of life. Thirty-two percent of patients had Hirschsprung disease (HSCR) that was associated with longer polyalanine repetitions or non-polyalanine repeat expansion mutations (NPARMs). Polyalanine repeat expansion mutations (PARMs) were more frequent and two novel NPARMs (c.780dupT and C.225–256delCT) were described in 14% of patients. Focal epilepsy was first described in 14% of patients and neurocognitive and neuromotor impairment involved 27% and 23% of children, respectively. Symptoms due to autonomic nervous system dysfunction/dysregulation (ANSD)—including strabismus (27%), dysphagia (27%), abnormal heart rhythm (10%), breath-holding spells (9%), and recurrent seizures due to hypoglycemia (9%)—were associated with an increased number of polyalanine repetitions of exon 3 or NPARMs of PHOX2B gene. Overall, the number of patients with moderate to severe phenotype initially treated with non-invasive ventilation (NIV) increased over time, and the decannulation program was concluded with 3 patients who started with IMV.Conclusions: Our study confirms that more severe phenotypes of CCHS are related to the number of polyalanine repetitions or to NPARMs. Although invasive ventilation is often required by patients with severe genotype/phenotype, gradual acquisition of specific skills in the management of patients with CCHS and technological improvements in mechanical ventilation allowed us to improve our therapeutic approach in this population.

A Common 3'UTR Variant of the PHOX2B Gene Is Associated With Infant Life-Threatening and Sudden Death Events in the Italian Population.

Heterozygous mutations in the Paired like homeobox 2b (PHOX2B) gene are causative of congenital central hypoventilation syndrome (CCHS), a rare monogenic disorder belonging to the family of neurocristopathies and due to a defective development of the autonomic nervous system. Most patients manifest sudden symptoms within 1 year of birth, mainly represented by central apnea and cyanosis episodes. The sudden appearance of hypoxic manifestations in CCHS and their occurrence during sleep resemble two other unexplained perinatal disorders, apparent life-threatening event (ALTE) and sudden and unexpected infant death (SUID), among which the vast majority is represented by sudden infant death syndrome (SIDS). Differently from CCHS, characterized by Mendelian autosomal dominant inheritance, ALTE and SIDS are complex traits, where common genetic variants, together with external factors, may exert an additive effect with symptoms likely manifesting only over a “threshold.” Given the similarities observed among the three abovementioned perinatal disorders, in this work, we have analyzed the frequency of PHOX2B common variants in two groups of Italian idiopathic ALTE (IALTE) and SUIDs/SIDS patients. Here, we report that the c*161G>A (rs114290493) SNP of the 3′UTR PHOX2B (i) became overrepresented in the two sets of patients compared to population matched healthy controls, and (ii) associated with decreased PHOX2B gene expression, likely mediated by miR-204, a microRNA already known to bind the 3′UTR of the PHOX2B gene. Overall, these results suggest that, at least in the Italian population, the SNP c*161G>A (rs114290493) does contribute, presumably in association with others mutations or polymorphisms, to confer susceptibility to sudden unexplained perinatal life-threatening or fatal disorders by increasing the effect of miR-204 in inducing PHOX2B expression down-regulation. However, these are preliminary observations that need to be confirmed on larger cohorts to achieve a clinical relevance.