PHOX2B Research Articles

The relative contributions of genetic and non‐genetic factors to the risk of neuroblastoma

ABSTRACTPrevious literature has well‐established genetic factors as being associated with neuroblastoma (NB). About 1%–2% of NB cases are familial, with 85% of these cases predisposed to mutations in the PHOX2B and ALK genes. The genetic basis of sporadic NB has been studied through genome‐wide association studies and next‐generation sequencing approaches. Particularly, germline variants, as well as copy number variations, confer increased risks of NB, often with effect estimates ≥1.5, underscoring the strong genetic contributions to NB. However, the strength of the association varied in non‐genetic factors. Some risk factors, such as birth defects, maternal illicit drug use, and early infections, had relatively stronger associations (effect estimates ≥1.5 or ≤0.67), while some other factors remain inconclusive. This suggests that certain non‐genetic factors may play a more prominent role in NB risk, while further research is needed to clarify the impact of others. We synthesized and critically evaluated existing literature on the risk factors of NB to provide an overview, analyze the current state of knowledge, and outline a research path to address the relative contributions of genetic and non‐genetic factors in NB. Future epidemiologic studies should incorporate novel methods for measuring genetic and non‐genetic factors to comprehensively assess the full extent of factors contributing to NB. Furthermore, the utilization of dried blood spots holds promise to overcome technical and recruitment challenges for future studies. These strategies will contribute to a more holistic understanding of NB etiology and potentially lead to improved prevention strategies.

Congenital Central Hypoventilation Syndrome: neonatal diagnosis and management

To report a neonatal case successfully treated with non-invasive ventilatory support (NVS), avoiding tracheostomy. Full-term newborn, whose mother uses nocturnal NVS due to CCHS. During the transition period, she presented desaturations associated with hypercapnia and respiratory acidosis, without pulmonary involvement. She developed severe hypoventilation during sleep, with no respiratory effort, peripheral oxygen saturation (SpO2) < 80%, plus respiratory acidosis. While awake, she had good respiratory effort and normal SpO2 without assistance. Noninvasive continuous positive airway pressure and oxygen therapy worsened her condition while sleeping. Complete NVS with nasal interface and bi-level airway positive pressure, inspiratory/expiratory pressure 14-16/4 cm H2O, normalized SpO2 during sleep, and arterial blood gases while awake. Sequencing of the PHOX2B gene confirmed the presence of a heterozygous pathogenic variant with the 20/26 genotype. At 2 months of age, she was discharged maintaining NVS with nasal interface and 0 PEEP, achieving adequate neurodevelopment. We highlight the importance of genetic diagnosis of CCHS in neonates with clinical presentation of early alveolar hypoventilation, especially if there is a family history. We are not aware of other reports of neonatal onset in which NVS prevents IMV, in this potentially lethal pathology.

Congenital central hypoventilation syndrome in korea: 20 years of clinical observation and evaluation of the ventilation strategy in a single center

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder characterized by hypoventilation due to impaired breathing control by the central nervous system and other symptoms of autonomic dysfunction. Mutations in paired-like homeobox 2 B (PHOX2B) are responsible for most cases of CCHS. Patients with CCHS have various phenotypes and severities, making the diagnosis difficult. This study aimed to present a comprehensive single-center experience of patients with CCHS, including key clinical features, treatment strategies, and outcomes. A retrospective chart review was performed for patients diagnosed with CCHS between January 2001 and July 2023 at Seoul National University Children’s Hospital. Finally, we selected 24 patients and collected their demographic data, genotypes, ventilation methods, and clinical features related to autonomic dysfunction. The relationship between the clinical manifestations and genotypes was also examined. All patients used home ventilators, and tracheostomy was performed in 87.5% of patients. Fifteen (62.5%) patients had constipation and nine (37.5%) were diagnosed with Hirschsprung disease. Arrhythmia, endocrine dysfunction, and subclinical hypothyroidism were present in nine (37.5%), six patients (25.0%), and two patients (16.7%), respectively. A significant number of patients exhibited neurodevelopmental delays (19 patients, 79.2%). There was a correlation between the phenotype and genotype of PHOX2B in patients with CCHS. (r = 0.71, p < 0.001). Conclusion: There was a positive correlation between paired-like homeobox 2 B mutations (especially the number of GCN repeats in the polyalanine repeat mutations sequence) and clinical manifestations. This study also demonstrated how initial treatment for hypoventilation affects neurodevelopmental outcomes in patients with CCHS.What is Known:• Congenital central hypoventilation syndrome is a rare genetic disorder characterized by hypoventilation and dysfunction of autonomic nervous system.• The disease-defining gene of CCHS isPHOX2Bgene – most of the cases have heterozygous PARMs and the number of GCN triplets varies among the patients(20/24 – 20/33).What is New:• We have noted in the Korean patients with CCHS that there is a correlation between genotype (number of GCN repeats) and severity of phenotype.• National support for rare diseases allowed for a prompter diagnosis of patients with CCHS in Korean population.

Primitive Embryonic-Type Neuroectodermal/Glandular Complexes in Testicular Germ Cell Tumors: A Mimic of Embryonic-Type Neuroectodermal Tumor.

Embryonic-type neuroectodermal elements are often intimately mixed with primitive endodermal-type glands, like those of yolk sac tumors, in germ cell neoplasia in situ (GCNIS)-derived germ cell tumors of the testis. Because the primitive glands mimic tubules or rosettes of embryonic-type neuroectodermal elements, these embryonic-type neuroectodermal/glandular complexes may be misinterpreted as pure lesions of embryonic-type neuroectodermal elements, which, if of sufficient size, may lead to a diagnosis of embryonic-type neuroectodermal tumor, despite that the criteria of the World Health Organization for a "somatic-type malignancy" are not met. A diagnosis of embryonic-type neuroectodermal tumor in the testis may lead to retroperitoneal lymphadenectomy even in clinical stage I patients, and in postchemotherapy resections indicates a poor prognosis. The distinction of the neuroectodermal and glandular elements is not always straightforward based on morphology alone. We, therefore, studied 34 testis-derived germ cell tumors with embryonic-type neuroectodermal/glandular complexes and 2 purely glandular yolk sac tumors to characterize the immunophenotypes and determine an efficient immunohistochemical panel to aid in this differential. We found that GFAP, synaptophysin, and paired-like homeobox 2B (PHOX2B) expression was specific to embryonic-type neuroectodermal elements, although PHOX2B had poor sensitivity. In contrast, positive reactions with antibodies directed against AFP, villin, and CDX2 were specific for the glandular elements, although CDX2 had poor sensitivity. Other markers, including AE1/AE3 cytokeratin, SALL4, glypican 3, SOX2, SOX11, CD56, INSM1, and neurofilament, proved less helpful because of their nonspecificity and/or poor sensitivity. We conclude that the optimal immunohistochemical panel for distinguishing the components of embryonic-type neuroectodermal/glandular complexes includes stains for synaptophysin, GFAP, villin, and AFP.

Defective exercise-related expiratory muscle recruitment in patients with PHOX2B mutations: A clue to neural determinants of the congenital central hypoventilation syndrome

Introduction and objectivesThe human congenital central hypoventilation syndrome (CCHS) is caused by mutations in the PHOX2B (paired-like homeobox 2B) gene. Genetically engineered PHOX2B rodents exhibit defective development of the brainstem retrotrapezoid nucleus (RTN), a carbon dioxide sensitive structure that critically controls expiratory muscle recruitment. This has been linked to a blunted exercise ventilatory response. Whether this can be extrapolated to human CCHS is unknown and represents the objective of this study. Materials and methodsThirteen adult CCHS patients and 13 healthy participants performed an incremental symptom-limited cycle cardiopulmonary exercise test. Responses were analyzed using guideline approaches (ventilation V'E, tidal volume VT, breathing frequency, oxygen consumption, carbon dioxide production) complemented by a breathing pattern analysis (i.e. expiratory and inspiratory reserve volume, ERV and IRV). ResultsA ventilatory response occurred in both study groups, as follows: V'E and VT increased in CCHS patients until 40 W and then decreased, which was not observed in the healthy participants (p<0.001). In the latter, exercise-related ERV and IRV decreases attested to concomitant expiratory and inspiratory recruitment. In the CCHS patients, inspiratory recruitment occurred but there was no evidence of expiratory recruitment (absence of any ERV decrease, p<0.001). ConclusionsAssuming a similar organization of respiratory rhythmogenesis in humans and rodents, the lack of exercise-related expiratory recruitment observed in our CCHS patients is compatible with a PHOX2B-related defect of a neural structure that would be analogous to the rodents' RTN. Provided corroboration, ERV recruitment could serve as a physiological outcome in studies aiming at correcting breathing control in CCHS.

Computer-aided diagnostic screen for Congenital Central Hypoventilation Syndrome with facial phenotype.

Congenital Central Hypoventilation Syndrome (CCHS) has devastating consequences if not diagnosed promptly. Despite identification of the disease-defining gene PHOX2B and a facial phenotype, CCHS remains underdiagnosed. This study aimed to incorporate automated techniques on facial photos to screen for CCHS in a diverse pediatric cohort to improve early case identification and assess a facial phenotype-PHOX2B genotype relationship. Facial photos of children and young adults with CCHS were control-matched by age, sex, race/ethnicity. After validating landmarks, principal component analysis (PCA) was applied with logistic regression (LR) for feature attribution and machine learning models for subject classification and assessment by PHOX2B pathovariant. Gradient-based feature attribution confirmed a subtle facial phenotype and models were successful in classifying CCHS: neural network performed best (median sensitivity 90% (IQR84%, 95%)) on 179 clinical photos (versus LR and XGBoost, both 85% (IQR75-76%, 90%)). Outcomes were comparable stratified by PHOX2B genotype and with the addition of publicly available CCHS photos (n = 104) using PCA and LR (sensitivity 83-89% (IQR67-76%, 92-100%). Utilizing facial features, findings suggest an automated, accessible classifier may be used to screen for CCHS in children with the phenotype and support providers to seek PHOX2B testing to improve the diagnostics. Facial landmarking and principal component analysis on a diverse pediatric and young adult cohort with PHOX2B pathovariants delineated a distinct, subtle CCHS facial phenotype. Automated, low-cost machine learning models can detect a CCHS facial phenotype with a high sensitivity in screening to ultimately refer for disease-defining PHOX2B testing, potentially addressing gaps in disease underdiagnosis and allow for critical, timely intervention.

Characteristics and outcomes in children with congenital central hypoventilation syndrome on long-term mechanical ventilation in the Netherlands.

Our study results suggest that in our cohort, the genotype is not easily associated to the phenotype in CCHS. Consistent with these findings and international literature, we recommend a thorough annual evaluation for all patients with CCHS to ensure optimal management and follow-up. • The majority of CCHS patients are dependent on ventilatory support. • Variants in the PHOX2B gene are responsible for the characteristics of CCHS. • This study provides insight into the clinical course and long-term outcomes of CCHS patients in the Netherlands. • In CCHS, the genotype is not easily associated with the phenotype, requiring a thorough life-long follow-up for all patients.

Expression Pattern of Tumor-associated Antigens in Neuroblastoma: Association With Cytogenetic Features and Survival.

The prognosis of high-risk and relapsed neuroblastoma (NB) patients remains poor. The identification of tumor-associated markers is important for differential diagnosis, prognosis, and the development of targeted therapies. The aim of the study was to determine the expression profile of nine most common NB antigens and assess their association with clinicopathological characteristics and patient survival. Tumor samples from 86 patients with NB were evaluated for the expression of tumor-associated antigen (TAA) using quantitative PCR. Twenty-one patients with benign tumors and 17 healthy donors were assigned as controls. Overexpression of tyrosine hydroxylase (TH), PHOX2B, PRAME, GPC2, B7-H3, and Survivin is the most typical for NB. Positive expression of MAGEA3, MAGEA1, and NY-ESO-1 at low levels was detected in 54%, 48%, and 52%, respectively, and was not NB specific. Higher TH expression was observed in samples without MYCN-amplification, while higher expression of Survivin, PHOX2B, and GPC2 was significantly associated with the presence of 1p.36 deletion. Overexpression of TH, PHOX2B, and MAGEA1 was associated with better event-free (EFS) and overall survival (OS). Survivin overexpression was associated with poor EFS but had no impact on OS. Multivariate analysis confirmed Survivin as independent marker for poor survival, and PHOX2B and MAGEA1 for better survival. High expression of TH, PHOX2B, and MAGEA1 genes are favorable prognostic factors for OS and EFS, whereas high expression of Survivin is associated with an increased risk of relapse or progression.

Congenital Central Hypoventilation Syndrome (Ondine’s Curse): Clinical Case

Background. Congenital central hypoventilation syndrome (CCHS), or Ondine’s Curse, is rare, incurable and life-threatening disease characterized by autonomic nervous system disorders, it manifests with disability to maintain ventilation function during sleep. Sensitivity to hypoxia and hypercapnia is reduced in case of CCHS, thus, it leads to recurrent episodes of deep apnea. The world literature describes just over 1000 cases of this disease. Clinical case description. An infant born at 37th week of gestation, weight of 3330 g, had episodes of apnea and hypercapnia from the first day of life. CCHS was suspected by the 28th day of life after excluding other causes of respiratory disorders, and it was genetically confirmed by the 43rd day of life — pathogenic variant of PHOX2B gene was revealed. Mechanical ventilation has been initiated by the age of 1 month after disease worsening. Analysis of CCHS cases published in Russian-language medical literature was performed. Typical symptoms and timing of their manifestation, as well as the time before correct diagnosis were mentioned. Conclusion. Symptoms that can be suggestive of CCHS presence early after birth and can urge to perform all the necessary genetic testing that are crucial for timely treatment onset and for minimizing the negative effect of hypoxemia and hypercapnia on the child are described.

LncRNA FAM13A-AS1, transcriptionally regulated by PHOX2B, modulates hepatocellular carcinoma chemoresistance via stabilizing PPARγ

Hepatocellular carcinoma (HCC) is a major global public health concern, with approximately 79 million new cases and 75 million HCC-related deaths occurring annually worldwide. Among the drugs, cisplatin (DDP) is considered a cornerstone and has been shown to significantly inhibit cancer progression. However, the mechanism underlying DDP-resistance in HCC remains unclear. This study aimed to identify a novel lncRNA. FAM13A Antisense RNA 1 (FAM13A-AS1), that promotes the proliferation of DDP-resistant HCC cells and to elucidate its downstream and upstream mechanisms in the progression of HCC DDP-resistance. Our results suggest that FAM13A-AS1 interacts directly with Peroxisome Proliferator Activated Receptor γ (PPARγ), stabilizing its protein through de-ubiquitination. Moreover, our findings indicate that Paired Like Homeobox 2B (PHOX2B) transcriptionally regulates the expression of FAM13A-AS1 in HCC cells. These results shed new light on the understanding of the progression of HCC DDP-resistance.

Congenital Central Hypoventilation Syndrome in Israel-Novel Findings from a New National Center.

Congenital central hypoventilation syndrome (CCHS) is a rare autosomal-dominant disorder of the autonomic nervous system that results from mutations in the PHOX2B gene. A national CCHS center was founded in Israel in 2018. Unique new findings were observed. All 27 CCHS patients in Israel were contacted and followed. Novel findings were observed. The prevalence of new CCHS cases was almost twice higher compared to other countries. The most common mutations in our cohort were polyalanine repeat mutations (PARM) 20/25, 20/26, 20/27 (combined = 85% of cases). Two patients showed unique recessive inheritance while their heterozygotes family members were asymptomatic. A right-sided cardio-neuromodulation was performed on an eight-year-old boy for recurrent asystoles by ablating the parasympathetic ganglionated plexi using radiofrequency (RF) energy. Over 36 months' follow-up with an implantable loop-recorder, no bradycardias/pauses events were observed. A cardiac pacemaker was avoided. A significant benefit and new information arise from a nationwide expert CCHS center for both clinical and basic purposes. The incidence of CCHS in some populations may be increased. Asymptomatic NPARM mutations may be much more common in the general population, leading to an autosomal recessive presentation of CCHS. RF cardio-neuromodulation offers a novel approach to children avoiding the need for permanent pacemaker implantation.

Evaluation of iodine-123-labeled metaiodobenzylguanidine single-photon emission computed tomography/computed tomography based on the International Society of Pediatric Oncology Europe Neuroblastoma score in children with neuroblastoma.

This study sought to examine whether iodine-123-labeled metaiodobenzylguanidine (123I-MIBG) single-photon emission computed tomography/computed tomography (SPECT/CT), which is based on the International Society of Pediatric Oncology Europe Neuroblastoma (SIOPEN) score, could improve the diagnostic efficiency of children with neuroblastoma (NB), and to compare the diagnostic ability of minimal residual disease (MRD) detection and 123I-MIBG SPECT/CT. We retrospectively analyzed 238 scans of patients who underwent 123I-MIBG SPECT/CT at the Department of Nuclear Medicine, Beijing Friendship Hospital, from January 2021 to December 2021. The diagnostic study was not registered with a clinical trial platform, and the study protocol was not published. The standard was established based on pathology, other relevant imaging examinations, and follow-up. The SIOPEN scores were calculated separately based on planar and tomographic imaging. In a comparison to the standard mentioned in the method, the diagnostic accuracy of planar and tomographic imaging was 151 of 238 (63.5%) and 228 of 238 (95.8%), respectively, and the κ values of the SIOPEN score were 0.468 and 0.855 (P<0.001), respectively. The SIOPEN scores differed significantly among the various subgroups. The polymerase chain reaction (PCR) method used to detect the bone marrow PHOX2B gene was able to find bone/bone marrow metastases (P=0.024, κ=0.282), while the flow cytometry (FCM) assay method was not statistically significant (P=0.417, κ=0.065). 123I-MIBG SPECT/CT, which relies on the semiquantitative assessment of the SIOPEN score, is of clinical importance in the management of pediatric NB. MRD detection can be used to detect early metastasis and recurrence in the bone or bone marrow; however, 123I-MIBG SPECT/CT has better diagnostic value. We intend to conduct further investigations on their prognostic value in the future.

0901 An odd presentation of a hidden curse

Abstract Introduction Congenital central hypoventilation syndrome (CCHS) is a rare disorder of respiratory deficiency due to a mutation in the PHOX2B gene. Clinical presentation may be mild in certain individuals due to different levels of ventilatory dysregulation. Methods We present the findings of exogenous ventilatory challenge testing and polysomnography (PSG) performed on a normocapnic adult female with late-onset (LO) CCHS patient. Results The patient was exposed to four separate ventilatory challenges. During exposure to hyperoxia using 100% oxygen (O2) administration, patient showed an inconsistent ventilatory response with a blunted and delayed increase in regional tissue oxygen saturation (rSO2). During hyperoxic hypercapnia with 5% carbon dioxide (CO2) and 95% O2, she demonstrated a reduced ventilatory response based on respiratory rate and tidal volume. During hypoxic hypercapnia, 7% CO2 and 14% O2, patient demonstrated a delayed and markedly attenuated ventilatory response. Hypoxia; 100% nitrogen inhalation did not result in increased ventilation. Ve slope, change in minute ventilation/change in end-tidal CO2 (EtCO2), with hypercapnia challenges was 4.88, which is lower than normal. Ventilatory EtCO2 threshold was 36 mmHg. PSG showed apnea-hypopnea index 3.3 with hypoxemia during rapid eye movement (REM), with an oxygen saturation nadir of 84%. EtCO2 baseline was around 36, peak was 50 and was associated with REM-related apnea events. Arterial blood gas was unremarkable. Conclusion CCHS is characterized by abnormal respiratory response to exogenous ventilatory challenge testing. Hyperoxia silences peripheral chemoreceptors (PC) responsible for stimulating ventilation in normal individuals. Hyperoxic hypercapnia silences PC but stimulates central chemoreceptors (CC). Hypoxic hypercapnia stimulates hyperventilation via both PC and CC. Our patient demonstrated inconsistent and reduced ventilatory responses to all four challenges. As expected, the classic chemosensory parameter, Ve slope, for hypercarbia challenge was markedly reduced. However, the ventilatory EtCO2 threshold fell well below threshold typically observed in CCHS. PSG noted greater alveolar hypoventilation during REM compared to non-REM, which is also atypical for CCHS. In conclusion, exogenous ventilatory challenge testing demonstrated derangements in ventilatory control typical in CCHS. Despite this, our patient had no evidence of daytime hypoventilation with normal CO2 threshold. This case illustrates the phenotypic variability present in LO-CCHS. Support (if any)

1028 Congenital Central Hypoventilation in a patient with MCEP2 duplication syndrome

Abstract Introduction Congenital central hypoventilation (CCHS) is a rare disorder due to impairment of autonomic nervous system clinically defined by a significantly reduced or abolished ventilatory response to hypercapnia and hypoxemia in the absence of pulmonary, neuromuscular, or cardiac disease. There is limited knowledge on associated respiratory manifestations and sleep-disordered breathing in children with the MECP2 duplication syndrome. Although sleep-disordered breathing and nocturnal hypoventilation are currently not well recognized in these children, we present a case of a patient with MECP2 mutation and congenital hypoventilation syndrome. Report of case(s) 24-week-old male born full-term via c-section presented with recurrent respiratory problems, laryngeal cleft, dysphagia, snoring and apneic episodes. Previous genetic work up showed chromosome 15q11.2 microdeletion. Past medical history was significant for neonatal ICU stay for respiratory distress immediately following birth. Tonsils are 1+ on exam. PSG showed profound central sleep apnea (CAI 300/h) with average apneic episodes lasted for 7 seconds and very significant periodic breathing (88%) and mild obstructive apnea. Mild hypoxemia was also seen with SpO2 in low 90s without any significant hypercapnia. Bradypnea with resp rate 10-20/m was seen. PHOX2B gene testing was negative. Genetic testing with SNP array showed MECP2 duplication syndrome. His development is delayed, currently at the age of 20 months, including cognitive, speech and motor function for which he is on therapy. Tracheostomy was recommended, however family preferred to continue with non-invasive ventilation while awaiting diaphragmatic pacing. Conclusion Respiratory manifestations in MECP2 duplication syndrome patients are common, with important impact and even a possible fatal outcome. Although sleep-disordered breathing and nocturnal hypoventilation is currently not cited as an important symptom in these children, there have been several case reports of CCHS associated with this. PSG should be considered in patients with MCEP2 duplication syndrome for timely diagnosis. Different treatment modalities (ENT surgery, CPAP and NIV) can be applied successfully to treat respiratory conditions associated with MECP2 duplication syndrome. Support (if any)

1034 A Rare Case of ROHHAD Syndrome

Abstract Introduction Early diagnosis of pediatric syndromes that are rare and involve multiple systems can be challenging. Rapid onset obesity, hypoventilation, hypothalamic dysfunction, and autonomic dysregulation characterizes ROHHAD syndrome which, if undiagnosed, can lead to potentially harmful outcomes including deferring radiological workup for a neural crest tumor (which has an over 50% association) and cardiopulmonary arrest. Report of case(s) A 10-year-old female with a history of obesity, precocious puberty, recurrent hypothermia, recurrent sodium derangements, bilateral ptosis, seizure disorder, and GERD initially presented to sleep clinic as a 4-year-old in 2017 when she recently began snoring with excessive daytime sleepiness as a result of rapid onset of weight gain. BMI at that time was 99th percentile and Epworth was 11. An in-lab polysomnography revealed severe OSA with AHI 26.4 events/hour; nocturnal hypoxemia with TS90 27% and O2 nadir 70%; and sleep related hypoventilation based on elevated pCO2 on end-tidal capnometry. Patient underwent adenotonsillectomy, revision adenoidectomy, and was started on CPAP before transitioning to BiPAP over the span of the next several years with serial polysomnographies ultimately showing significant improvement of sleep apnea with AHI 5.4 events/hour. Sleep-related hypoventilation, however, remained persistent with blood gases showing pCO2 as high as 89. PHOX2B gene testing was negative and secondary causes of hypoventilation were ruled out. During this time, she was also followed by Endocrinology for suspected hypothalamic dysfunction resulting in precocious puberty, deceleration of growth rate, sodium derangements. Autonomic dysfunction was also suspected due to recurrent hypothermia including a recent admission for Temperature &amp;lt; 95F and ophthalmologic abnormalities including bilateral ptosis. At a multidisciplinary care conference, a working diagnosis of ROHHAD syndrome was made based on the rapid onset of obesity, hypoventilation on sleep studies and CBGs, hypothalamic dysfunction, and autonomic degeneration. Workup for neural crest tumor with MRI chest and abdomen unremarkable. Outside academic consultation was sought for management which recommended shared decision-making regarding steroids, immunosuppressive therapy (eg rituximab, cyclophosphamide), and IVIG. Conclusion For ROHHAD syndrome, there are very few documented cases in the United States and there is no known laboratory marker; diagnosis remains clinical and takes multidisciplinary collaboration, education, and a high degree of suspicion. Support (if any)

Congenital central hypoventilation syndrome (Ondine’s curse)

Pediatricians and neonatologists often deal with a variety of causes of respiratory failure. Most algorithms for the diagnosis and treatment of such conditions are well developed. However, the diagnosis of some rare causes of respiratory disorders is still challenging. The aim of this review is to present current literature data on a very rare autosomal dominant disorder – congenital central hypoventilation syndrome (Ondine’s curse). This syndrome is manifested by the absence of spontaneous breathing due to a congenital genetic defect, namely the expansion of the polyalanine tract in the PHOX2B gene on chromosome 4p12. Conclusion. Issues of pathogenesis, diagnosis, clinical variants, treatment, and prognosis of this disease are discussed.

EGR4 is critical for cell-fate determination and phenotypic maintenance of geniculate ganglion neurons underlying sweet and umami taste

The sense of taste starts with activation of receptor cells in taste buds by chemical stimuli which then communicate this signal via innervating oral sensory neurons to the CNS. The cell bodies of oral sensory neurons reside in the geniculate ganglion (GG) and nodose/petrosal/jugular ganglion. The geniculate ganglion contains two main neuronal populations: BRN3A+ somatosensory neurons that innervate the pinna and PHOX2B+ sensory neurons that innervate the oral cavity. While much is known about the different taste bud cell subtypes, considerably less is known about the molecular identities of PHOX2B+ sensory subpopulations. In the GG, as many as 12 different subpopulations have been predicted from electrophysiological studies, while transcriptional identities exist for only 3 to 6. Importantly, the cell fate pathways that diversify PHOX2B+ oral sensory neurons into these subpopulations are unknown. The transcription factor EGR4 was identified as being highly expressed in GG neurons. EGR4 deletion causes GG oral sensory neurons to lose their expression of PHOX2B and other oral sensory genes and up-regulate BRN3A. This is followed by a loss of chemosensory innervation of taste buds, a loss of type II taste cells responsive to bitter, sweet, and umami stimuli, and a concomitant increase in type I glial-like taste bud cells. These deficits culminate in a loss of nerve responses to sweet and umami taste qualities. Taken together, we identify a critical role of EGR4 in cell fate specification and maintenance of subpopulations of GG neurons, which in turn maintain the appropriate sweet and umami taste receptor cells.

Phox2ba: The Potential Genetic Link behind the Overlap in the Symptomatology between CHARGE and Central Congenital Hypoventilation Syndromes.

CHARGE syndrome typically results from mutations in the gene encoding chromodomain helicase DNA-binding protein 7 (CHD7). CHD7 is involved in regulating neural crest development, which gives rise to tissues of the skull/face and the autonomic nervous system (ANS). Individuals with CHARGE syndrome are frequently born with anomalies requiring multiple surgeries and often experience adverse events post-anesthesia, including oxygen desaturations, decreased respiratory rates, and heart rate abnormalities. Central congenital hypoventilation syndrome (CCHS) affects ANS components that regulate breathing. Its hallmark feature is hypoventilation during sleep, clinically resembling observations in anesthetized CHARGE patients. Loss of PHOX2B (paired-like homeobox 2b) underlies CCHS. Employing a chd7-null zebrafish model, we investigated physiologic responses to anesthesia and compared these to loss of phox2b. Heart rates were lower in chd7 mutants compared to the wild-type. Exposure to tricaine, a zebrafish anesthetic/muscle relaxant, revealed that chd7 mutants took longer to become anesthetized, with higher respiratory rates during recovery. chd7 mutant larvae demonstrated unique phox2ba expression patterns. The knockdown of phox2ba reduced larval heart rates similar to chd7 mutants. chd7 mutant fish are a valuable preclinical model to investigate anesthesia in CHARGE syndrome and reveal a novel functional link between CHARGE syndrome and CCHS.

0994 Neuroblastoma as the Initial Manifestation of Familial PHOX2B NPARM Positive Congenital Central Hypoventilation Syndrome

Abstract Introduction Congenital Central Hypoventilation Syndrome (CCHS) is a genetic disorder of the autonomic nervous system caused by mutations in the PHOX2B gene. Children with CCHS often present as neonates in hypoxemic, hypercarbic respiratory failure. Most causative mutations are de novo Polyalanine Repeat Mutations (PARMs). Non-Polyalanine Repeat Mutations (NPARMs) have been associated with more severe disease, specifically the need for 24-hour ventilatory support, Hirschsprung disease, and neural crest tumors; however, NPARMs may have variable expressivity and incomplete penetrance, resulting in delayed or atypical presentations. We report a toddler with maxillary sinus neuroblastoma, which led to the diagnosis of familial PHOX2B NPARM positive CCHS. Report of case(s) A two-year-old boy presented with right-sided facial swelling. A facial CT uncovered a right maxillary sinus lytic lesion, and biopsy confirmed neuroblastoma. After full recovery from the procedure, he had persistent nocturnal hypoxemia and hypercapnia requiring bilevel positive airway pressure (PAP) during sleep, raising concern for CCHS. Genetic testing revealed a novel PHOX2B NPARM, c.428dup, which likely causes a frameshift and premature protein termination (p.Val144Glyfs*34). His maternal grandfather, mother and brothers tested positive for the same mutation. Family history revealed that his maternal grandfather and maternal great-uncles had frequent childhood apneic spells associated with syncope, his maternal grandfather is currently on nocturnal bilevel PAP, and his mother almost drowned as a younger child while having a breath-holding contest under water. His six-year-old brother underwent polysomnography which showed hypoventilation, now managed with bilevel PAP. His five-year-old brother also underwent polysomnography and does not require nocturnal ventilatory support at this time. Conclusion We report a rare case of familial PHOX2B NPARM positive CCHS which initially presented as maxillary sinus neuroblastoma. Additionally, the child and his family display varying disease severity despite having the same NPARM, highlighting the variable expressivity in this novel NPARM. Support (if any) None

Staying alert with polyhydramnios; an Ondine syndrome case

Abstract Objectives Amniotic fluid is essential for proper fetal development. In the case of severe polyhydramnios associated with low fetal growth, a number of different underlying disorders must be considered. One such condition is congenital central hypoventilation syndrome (CCHS) or Ondine’s curse, a rare genetic disease caused by mutation of the PHOX2B gene. The incidence of CCHS is estimated to be 1 case in 200,000 live births. No publications have been made to date on the intrauterine period findings. This precludes an early intrauterine diagnosis and impedes ethically responsible therapeutic options. Case presentation A 37-year-old patient presented in her second pregnancy with a small for gestation fetus and severe polyhydramnios evidenced in the third trimester ultrasound (US) study. There were no previous signs of maternal diabetes or fetal abnormalities at US. During the immediate postpartum period, the newborn presented repeated apneas with cyanosis and hypo-responsiveness. Neonatal arterial blood gas testing revealed severe respiratory acidosis requiring orotracheal intubation and admission to the Neonatal Intensive Care Unit. Over the following days, all imaging and functional test findings were within normal ranges. A de novo pathogenic PHOX2B variant was identified. Conclusions Despite a high mortality rate, no neurological sequelae or other systemic diseases were recorded, thanks to multidisciplinary and coordinated follow-up.