Genotype-phenotype relationship in Japanese patients with congenital central hypoventilation syndrome

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 is PHOX2B gene - 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.

Congenital Central Hypoventilation Syndrome: A Case Report

Congenital central hypoventilation syndrome (CCHS) is a rare cause of apnea and hypoventilation requiring long-term multidisciplinary care. In this article, we report the case of a two-month-old female child who presented with recurrent apnea and cyanosis, requiring long-term ventilation. After ruling out other common causes of apnea like sepsis, metabolic disorders, and neuromuscular disorders, a genetic study was done, which confirmed the diagnosis of CCHS. The child was discharged on home oxygen therapy, and the parents were counseled about genetic testing and informed about the prognosis and requirement for home ventilation therapy, as well as parental testing.

Knockdown of PHOX2B in the retrotrapezoid nucleus reduces the central CO2 chemoreflex in rats

PHOX2B is a transcription factor essential for the development of different classes of neurons in the central and peripheral nervous system. Heterozygous mutations in the PHOX2B coding region are responsible for the occurrence of Congenital Central Hypoventilation Syndrome (CCHS), a rare neurological disorder characterised by inadequate chemosensitivity and life-threatening sleep-related hypoventilation. Animal studies suggest that chemoreflex defects are caused in part by the improper development or function of PHOX2B expressing neurons in the retrotrapezoid nucleus (RTN), a central hub for CO2 chemosensitivity. Although the function of PHOX2B in rodents during development is well established, its role in the adult respiratory network remains unknown. In this study, we investigated whether reduction in PHOX2B expression in chemosensitive neuromedin-B (NMB) expressing neurons in the RTN altered respiratory function. Four weeks following local RTN injection of a lentiviral vector expressing the short hairpin RNA (shRNA) targeting Phox2b mRNA, a reduction of PHOX2B expression was observed in Nmb neurons compared to both naive rats and rats injected with the non-target shRNA. PHOX2B knockdown did not affect breathing in room air or under hypoxia, but ventilation was significantly impaired during hypercapnia. PHOX2B knockdown did not alter Nmb expression but it was associated with reduced expression of both Task2 and Gpr4, two CO2/pH sensors in the RTN. We conclude that PHOX2B in the adult brain has an important role in CO2 chemoreception and reduced PHOX2B expression in CCHS beyond the developmental period may contribute to the impaired central chemoreflex function.

Pulmonary hypertension in an adult patient with congenital central hypoventilation syndrome: a case report

Background

Congenital central hypoventilation syndrome (CCHS) is a life-threatening disorder of autonomic respiratory control. Mutations in the paired-like homeobox 2B (PHOX2B) gene impair respiratory drive, causing hypercarbia and hypoxaemia. Most patients with CCHS are diagnosed in the neonatal period; however, a few are diagnosed in adulthood.

Case summary

We report a 32-year-old man with a history of unexplained cyanosis 14 days after birth. He presented to our hospital with breathlessness and abnormal electrocardiogram findings discovered in a health check-up. Pulmonary hypertension (PH) was suspected based on electrocardiographic and echocardiographic evidence of right ventricular (RV) overload. Results of pulmonary function tests and chest computed tomography were normal. Arterial blood gas analysis revealed type 2 respiratory failure without a significant alveolar-arterial oxygen gradient, indicating alveolar hypoventilation. Right heart catheterization (RHC) showed pre-capillary PH [pulmonary artery pressure 47/24 (35) mmHg], and a hyperventilation challenge test and a non-invasive positive pressure ventilation (NPPV) treatment during RHC provided drastic improvement in PH [pulmonary artery pressure 28/12 (18) mmHg]. Congenital central hypoventilation syndrome was diagnosed based on genetic testing (20/25 polyalanine repeat expansion mutations in PHOX2B). After NPPV therapy initiation, the RV overload was slightly improved.

Discussion

Some patients with CCHS develop mild hypoventilation without overt clinical signs, and PH can be the first clinical manifestation. In our case, the hyperventilation challenge test improved PH. Although CCHS causes chronic alveolar hypoxia and hypoxic pulmonary vasoconstriction with subsequent PH, optimal ventilation therapy can improve pulmonary circulation even in affected adults.

Elevated transaminases in congenital central hypoventilation syndrome

Patients with CCHS who also have Hirschsprung disease, elevated or low BMI, or pulmonary hypertension may be predisposed to elevated transaminases and may need periodic follow-up of their hepatic function https://bit.ly/3uW7AUG.

Congenital central hypoventilation syndrome in Chinese population: Analysis of three new cases and review of the literature

BACKGROUND

Congenital central hypoventilation syndrome (CCHS) is a rare autosomal dominant disease that is mainly caused by PHOX2B mutations. The purpose of this study is to analyze and summarize the clinical and genetic characteristics of CCHS patients in the Chinese population from our study and previous literature.

METHODS

The potential pathogenic gene mutations of CCHS were identified and verified by next generation sequencing combined with Sanger sequencing, fluorescent probe PCR and capillary electrophoresis. The clinical characteristics and gene mutations of CCHS cases in Chinese population were summarized from our study and previous literature to explore the genotype-phenotype correlations.

RESULTS

We identified 48 CCHS cases including three new cases from our report in China. Overall, 77.1% of the patients had PHOX2B polyalanine repeat expansion mutations (PARMs), and the remaining 22.9% had 10 distinct PHOX2B non-polyalanine repeat expansion mutations (NPARMs). Compared to those with PARMs, patients with NPARMs were more likely to have premature birth (54.5% vs. 2.8%, p < 0.001) and lower birth weight (33.3% vs. 3.2%, p = 0.030), with statistical significance. The patients with PARMs were more likely to have cardiovascular defects (64.9% vs. 27.3%, p = 0.063), cerebral hemorrhage (29.7% vs. 9.1%, p = 0.322) and seizures (37.8% vs. 9.1%, p = 0.151) than those with NPARMs, with no statistical significance.

CONCLUSIONS

CCHS patients with PHOX2B NPARMs were more likely to have premature birth and low birth weight, while PHOX2B PARMs tended to be positively associated with the risk of cardiovascular defects, cerebral hemorrhage and seizures in Chinese population.

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

BACKGROUND

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.

METHODS

All 27 CCHS patients in Israel were contacted and followed. Novel findings were observed.

RESULTS

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.

CONCLUSIONS

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.

Neurocognition as a biomarker in the rare autonomic disorders of CCHS and ROHHAD

PURPOSE

Congenital central hypoventilation syndrome (CCHS) and rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD) are rare disorders of autonomic regulation with risk for disrupted neurocognitive development. Our aim is to summarize research on neurocognitive outcomes in these conditions, advance understanding of how to best support these individuals throughout development, and facilitate future research.

METHODS

We conducted a narrative review of literature on neurocognitive outcomes in CCHS and ROHHAD, supplemented with previously unpublished data from patients with CCHS and ROHHAD at our Center for Autonomic Medicine in Pediatrics (CAMP).

RESULTS

Individuals with CCHS and ROHHAD experience a wide range of neurocognitive functioning ranging from above average to below average, but are at particular risk for difficulties with working memory, processing speed, perceptual reasoning, and visuographic skills. An assessment framework emphasizing fluid cognition seems especially appropriate for these conditions. Owing to small cohorts and varied methods of data collection, it has been difficult to identify associations between disease factors (including CCHS PHOX2B genotypes) and cognitive outcomes. However, results suggest that early childhood is a period of particular vulnerability, perhaps due to the disruptive impact of recurrent intermittent hypoxic episodes on brain and cognitive development.

CONCLUSION

Neurocognitive monitoring is recommended as a component of routine clinical care in CCHS and ROHHAD as a marker of disease status and to ensure that educational support and disability accommodations are provided as early as possible. Collaborative efforts will be essential to obtain samples needed to enhance our understanding of neurocognitive outcomes in CCHS and ROHHAD.

Transitional care and clinical management of adolescents, young adults, and suspected new adult patients with congenital central hypoventilation syndrome

PURPOSE

With contemporaneous advances in congenital central hypoventilation syndrome (CCHS), recognition, confirmatory diagnostics with PHOX2B genetic testing, and conservative management to reduce the risk of early morbidity and mortality, the prevalence of identified adolescents and young adults with CCHS and later-onset (LO-) CCHS has increased. Accordingly, there is heightened awareness and need for transitional care of these patients from pediatric medicine into a multidisciplinary adult medical team. Hence, this review summarizes key clinical and management considerations for patients with CCHS and LO-CCHS and emphasizes topics of particular importance for this demographic.

METHODS

We performed a systematic review of literature on diagnostics, pathophysiology, and clinical management in CCHS and LO-CCHS, and supplemented the review with anecdotal but extensive experiences from large academic pediatric centers with expertise in CCHS.

RESULTS

We summarized our findings topically for an overview of the medical care in CCHS and LO-CCHS specifically applicable to adolescents and adults. Care topics include genetic and embryologic basis of the disease, clinical presentation, management, variability in autonomic nervous system dysfunction, and clarity regarding transitional care with unique considerations such as living independently, family planning, exposure to anesthesia, and alcohol and drug use.

CONCLUSIONS

While a lack of experience and evidence exists in the care of adults with CCHS and LO-CCHS, a review of the relevant literature and expert consensus provides guidance for transitional care areas.

Ventilatory and Orthostatic Challenges Reveal Biomarkers for Neurocognition in Children and Young Adults With Congenital Central Hypoventilation Syndrome

BACKGROUND

Children and young adults with congenital central hypoventilation syndrome (CCHS) are at risk of cognitive deficits. They experience autonomic dysfunction and chemoreceptor insensitivity measured during ventilatory and orthostatic challenges, but relationships between these features are undefined.

RESEARCH QUESTION

Can a biomarker be identified from physiologic responses to ventilatory and orthostatic challenges that is related to neurocognitive outcomes in CCHS?

STUDY DESIGN AND METHODS

This retrospective study included 25 children and young adults with CCHS tested over an inpatient stay. Relationships between physiologic measurements during hypercarbic and hypoxic ventilatory challenges, hypoxic ventilatory challenges, and orthostatic challenges and neurocognitive outcomes (by Wechsler intelligence indexes) were examined. Independent variable inclusion was determined by significant associations in Pearson's analyses. Multivariate linear regressions were used to assess relationships between measured physiologic responses to challenges and neurocognitive scores.

RESULTS

Significant relationships were identified between areas of fluid intelligence and measures of oxygen saturation (SpO2) and heart rate (HR) during challenges. Specifically, perceptual reasoning was related to HR (adjusted regression [β] coefficient, -0.68; 95% CI, 1.24 to -0.12; P = .02) during orthostasis. Working memory was related to change in HR (β, -1.33; 95% CI, -2.61 to -0.05; P = .042) during the hypoxic ventilatory challenge. Processing speed was related to HR (β, -1.19; 95% CI, -1.93 to -0.46; P = .003) during orthostasis, to baseline SpO2 (hypercarbic and hypoxic β, 8.57 [95% CI, 1.63-15.51]; hypoxic β, 8.37 [95% CI, 3.65-13.11]; P = .002 for both) during the ventilatory challenges, and to intrachallenge SpO2 (β, 5.89; 95% CI, 0.71-11.07; P = .028) during the hypoxic ventilatory challenge.

INTERPRETATION

In children and young adults with CCHS, SpO2 and HR-or change in HR-at rest and as a response to hypoxia and orthostasis are related to cognitive outcomes in domains of known risk, particularly fluid reasoning. These findings can guide additional research on the usefulness of these as biomarkers in understanding the impact of daily physical stressors on neurodevelopment in this high-risk group.

Noninvasive ventilation via bilevel positive airway pressure improved sleep in a child with congenital central hypoventilation syndrome: A case report

We report the polysomnography findings of a 2-year-old girl who was previously diagnosed with CCHS and treated with bilevel positive airway pressure (BiPAP) and O2 supplementation for a year. The girl had convulsions 2 times in the last 10 days. After we replaced her nasal cannula with a nasal mask and adjusted the parameters of the BiPAP, her sleep and ventilation were improved. The polysomnographies measured under spontaneous breathing without oxygen supplementation showed that her sleep structure, heart rate, and oxygen saturation during sleep were improved 1 month and 1 year after effective BiPAP treatment.

A novel case of central hypoventilation syndrome or just heavy breathing?

With the growing prevalence of obesity in the pediatric population, reports of its severe complications are increasing. Obesity hypoventilation syndrome is an uncommon disorder in children with altered respiratory mechanics, sleep-disordered breathing, and impaired ventilatory responses leading to persistent hypercapnia. Presentation is varied, and children may remain relatively asymptomatic until challenged with a respiratory infection, when they may present with acute respiratory failure. With increasing use of genetic testing in pediatric patients, our knowledge of potential contributors to hypoventilation syndromes is growing. Although mutations in the paired-like homeobox 2B gene are known to be causative of congenital central hypoventilation syndrome, other genes may also contribute to hypoventilation phenotypes. We report one of the youngest reported patients with obesity hypoventilation syndrome in pediatrics, with a proposed congenital predisposition for central hypoventilation derived from a deletion in the brain-derived neurotrophic factor gene.

CITATION

McCoy J, Karp N, Brar J, Amin R, St-Laurent A. A novel case of central hypoventilation syndrome or just heavy breathing? J Clin Sleep Med. 2022;18(9):2321-2325.

Neurocognitive monitoring in congenital central hypoventilation syndrome with the NIH Toolbox®

Congenital central hypoventilation syndrome (CCHS) is a rare neurocristopathy, caused by mutations in the paired-like homeobox gene PHOX2B, which alters control of breathing and autonomic nervous system regulation, necessitating artificial ventilation as life-support. A broad range of neurocognitive performance has been reported in CCHS, including an array of cognitive deficits. We administered the NIH Toolbox® Cognition Battery (NTCB), a novel technology comprised of seven tasks presented via an interactive computer tablet application, to a CCHS cohort and studied its convergent and divergent validity relative to traditional clinical neurocognitive measures. The NTCB was administered to 51 CCHS participants, including a subcohort of 24 who also received traditional clinical neurocognitive testing (Wechsler Intelligence Scales). Age-corrected NTCB scores from the overall sample and subcohort were compared to population norms. Associations between NTCB indices and Wechsler Intelligence scores were studied to determine the convergent and divergent validity of the NTCB. NTCB test results indicated reduced Fluid Cognition, which measures new learning and speeded information processing (p < 0.001), but intact Crystallized Cognition, which measures past learning, in CCHS relative to population norms. Moderate to strong associations (r > 0.60) were found between age-corrected NTCB Fluid and Crystallized indices and comparable Wechsler indices, supporting the convergent and discriminant validity of the NTCB. Results reveal deficits of Fluid Cognition in individuals with CCHS and indicate that the NTCB is a valid and sensitive measure of cognitive outcomes in this population. Our findings suggest that the NTCB may play a useful role in tracking neurocognition in CCHS.

A Newborn Infant with Congenital Central Hypoventilation Syndrome and Pupillary Abnormalities: A Literature Review

We present a neonate with early onset apnea and bradycardia in the absence of primary cardiorespiratory and central nervous system disorders that eventually required chronic ventilator support starting at 6 hours of life. Molecular testing of paired-like homeobox 2b (PHOX2B) gene mutation confirmed the diagnosis of congenital central hypoventilation syndrome (CCHS). CCHS is a rare genetic disorder characterized by impaired central respiratory control with or without broad spectrum of autonomic nervous system (ANS) dysregulations. Ocular ANS dysregulation is a rare finding in CCHS individuals, and it is usually discovered later in life. However, the ophthalmic evaluation of this neonate on first day of life revealed persistent mild dilated oval pupils with limited light reactivity.

Genetic study of a patient with congenital central hypoventilation syndrome in Iran: a case report

BACKGROUND

Congenital central hypoventilation syndrome (CCHS) is an extremely rare genetic disorder characterized by Autonomic nervous system dysregulation caused by mutations in the PHOX2B gene. Here we introduce the first genetic analysis of a one-month-old CCHS baby girl in Iran.

METHODS AND RESULTS

Genetic analysis of the PHOX2B gene was performed by Sanger sequencing and interpreted using the American College of Medical Genetics and Genomics (ACMG) guideline. The results showed a heterozygous duplication in exon 3, causing a polyalanine repeat expansion mutation to 27 repeats in thePHOX2B gene (20/27 genotype).The patient's parents did not demonstrate this mutation on genetic studies.

CONCLUSIONS

According to the ACMG guideline, the mutation is pathogenic, and it was a denovo mutation in the family. The genetic study can help the family for prenatal diagnosis or pre-implantation diagnosis if the parents have gonadal mosaicism.

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

BACKGROUND

Congenital 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.

METHODS

We 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.

RESULTS

We 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.

CONCLUSIONS

This 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.

Evaluation of respiratory center function in congenital central hypoventilation syndrome by monitoring electrical activity of the diaphragm

BACKGROUND

A definitive diagnosis of congenital central hypoventilation syndrome (CCHS) is made by genetic testing. However, there are only a few examinations that warrant genetic testing. Electrical activity of the diaphragm (Edi) reflects neural respiratory drive from respiratory center to diaphragm. We evaluated the function of the respiratory center in CCHS by Edi monitoring.

METHODS

Monitoring of Edi was performed in six CCHS cases without mechanical ventilation. The monitoring time was 30 consecutive minutes from wakefulness to sleep. The TcPCO₂ or EtCO₂ and SpO₂ were recorded simultaneously.

RESULTS

The Edi peak during wakefulness was 14.0 (10.3-21.0) µV and the Edi peak during sleep was 6.7 (3.8-8.0) µV. The Edi peak during sleep was significantly lower than the Edi peak during wakefulness, and patients were in a state of hypoventilation. Although TcPCO₂ or EtCO₂ increased due to hypoventilation, an increase in the Edi peak that reflects central respiratory drive was not observed. ΔEdi/ΔCO₂ was -0.06μV/mmHg. Maximum EtCO₂ or TcPco₂ was 51 mmHg, and the average SpO₂ was 91.5% during monitoring.

CONCLUSIONS

We confirmed that Edi monitoring could evaluate the function of the respiratory center and reproduce the hypoventilation of CCHS. The present study suggested that Edi monitoring is a useful examination in deciding whether to perform genetic testing or not and it may lead to an early diagnosis of CCHS.

Research Advances on Therapeutic Approaches to Congenital Central Hypoventilation Syndrome (CCHS)

Congenital central hypoventilation syndrome (CCHS) is a genetic disorder of neurodevelopment, with an autosomal dominant transmission, caused by heterozygous mutations in the PHOX2B gene. CCHS is a rare disorder characterized by hypoventilation due to the failure of autonomic control of breathing. Until now no curative treatment has been found. PHOX2B is a transcription factor that plays a crucial role in the development (and maintenance) of the autonomic nervous system, and in particular the neuronal structures involved in respiratory reflexes. The underlying pathogenetic mechanism is still unclear, although studies in vivo and in CCHS patients indicate that some neuronal structures may be damaged. Moreover, in vitro experimental data suggest that transcriptional dysregulation and protein misfolding may be key pathogenic mechanisms. This review summarizes latest researches that improved the comprehension of the molecular pathogenetic mechanisms responsible for CCHS and discusses the search for therapeutic intervention in light of the current knowledge about PHOX2B function.

Neurocognition in Congenital Central Hypoventilation Syndrome: influence of genotype and ventilation method

BACKGROUND

Congenital Central Hypoventilation Syndrome (CCHS) is characterized by central hypoventilation due to abnormal autonomic control of breathing and global dysautonomia. Patients harbour heterozygous PHOX-2B gene mutations which are polyalanine repeats of various lengths in most of the cases. A few previous studies have reported learning difficulties and neuropsychological disorders in patients with CCHS. The aims of the present study were (1) to explore the intellectual abilities of a group of children with CCHS followed up in the centre of reference for CCHS in France using the Wechsler batteries of tests, (2) and to assess whether there was any association between CCHS characteristics and various domains of the intellectual functioning.

RESULTS

There were 34 consecutive patients (15 males, 19 females) of mean (SD) age of 7.8 (3.8) years, ranging from 4 to 16 years and 6 months. Mean score of full-scale intelligence quotient was 82 (20), being in the low average range. Indexes of working memory and processing speed were significantly lower as compared to the other Wechsler indexes. There were two important findings: (1) full-scale intelligence quotient as well as indexes of verbal comprehension and processing speed were significantly greater in patients with mask ventilation than in those with tracheostomy ventilation (p = 0.012, 0.032 and 0.042 respectively); (2) most interestingly, in the patients with polyalanine repeats mutations, all intellectual indexes negatively correlated with the number of polyalanine expansion, with statistical significance reached for indexes of fluid reasoning and working memory (R = - 0.449, p = 0.032 and R = - 0.562, p = 0.012 respectively).

CONCLUSIONS

CCHS increased the risk to develop neurocognitive deficiencies, affecting particularly speed of processing and working memory. Our results suggested that both genetics and ventilation method could be also involved in the physiopathology of neurocognitive impairment. Further investigations were required to untangle the complex underlying processes. Neurocognitive assessments should be performed regularly in children with CCHS in order to plan re-education programs, adapt school integration and improve quality of life.

Pregnancy in congenital central hypoventilation syndrome

BACKGROUND

Congenital central hypoventilation syndrome is a rare genetic disorder of autonomic regulation of breathing resulting from mutations in the paired-like homeobox gene. Individuals with congenital central hypoventilation syndrome demonstrate an absent or diminished physiological response to hypercapnia and hypoxia that is most severe during sleep and depend on mechanical ventilation to maintain normal gas exchange. Increased disease awareness and availability of paired-like homeobox gene testing has improved congenital central hypoventilation syndrome morbidity and mortality, and patients are now living into adulthood. During pregnancy, delivery, and the postpartum period, women with congenital central hypoventilation syndrome are vulnerable to developing respiratory insufficiency. Currently, there is no standardized approach to monitoring ventilatory status and anticipating the need for changes to existing ventilatory support for women with congenital central hypoventilation syndrome during pregnancy, labor, and delivery.

OBJECTIVE

This study aimed to characterize current practices for monitoring ventilatory status and managing ventilatory needs in women with congenital central hypoventilation syndrome during pregnancy; identify specific circumstances through which ventilation may be compromised during pregnancy, delivery, and postpartum; evaluate utilization of prenatal congenital central hypoventilation syndrome testing; and report any adverse pregnancy outcomes.

STUDY DESIGN

We conducted an anonymous cross-sectional survey of women with congenital central hypoventilation syndrome with current or prior pregnancy. The 26-item electronic questionnaire included questions on congenital central hypoventilation syndrome genotype; number and outcome of pregnancies; use of mechanical ventilation; and issues with or adjustments made to ventilation during pregnancy, delivery, and the postpartum period.

RESULTS

We received 10 responses. Three patients were not diagnosed with congenital central hypoventilation syndrome until after pregnancy and delivery. The 7 patients with a preexisting congenital central hypoventilation syndrome diagnosis reported information on 10 total pregnancies. At baseline, patients relied on various types of ventilatory support including positive pressure ventilation via tracheostomy, bilevel noninvasive positive pressure ventilation, and diaphragm pacing by phrenic nerve stimulation. Polysomnography for objective assessment of nocturnal ventilation was not consistently utilized. Changes to baseline ventilatory support were required during 3 out of 10 pregnancies. In addition, 2 patients using diaphragm pacing reported discomfort with pacing during the third trimester or after cesarean delivery, prompting discontinuation of diaphragm pacing. In 1 instance, discontinuation of diaphragm pacing and lack of recognition of need for an alternative support method led to respiratory arrest and need for emergent resuscitation. All patients who were offered prenatal congenital central hypoventilation syndrome testing chose to undergo testing. Of note, 9 out of 10 pregnancies were carried successfully to term and 5 infants were diagnosed with congenital central hypoventilation syndrome.

CONCLUSION

Women with congenital central hypoventilation syndrome may experience issues maintaining adequate ventilation during pregnancy, necessitating an adjustment of ventilator settings or use of an alternative type of ventilation. Objective assessment of nocturnal ventilation by means of polysomnography is an important part of congenital central hypoventilation syndrome pregnancy care to optimize maintenance of adequate gas exchange. Patients who rely on diaphragm pacing may experience discomfort with pacing during the later stages of pregnancy and after cesarean delivery. Anticipatory guidance and contingency planning for changing ventilatory needs should be discussed early in pregnancy. Prenatal congenital central hypoventilation syndrome testing should be offered to pregnant patients with congenital central hypoventilation syndrome to inform delivery decisions and prepare for the provision of advanced neonatal care.

Guidelines for diagnosis and management of congenital central hypoventilation syndrome

BACKGROUND

Congenital Central Hypoventilation Syndrome (CCHS) is a rare condition characterized by an alveolar hypoventilation due to a deficient autonomic central control of ventilation and a global autonomic dysfunction. Paired-like homeobox 2B (PHOX2B) mutations are found in most of the patients with CCHS. In recent years, the condition has evolved from a life-threatening neonatal onset disorder to include broader and milder clinical presentations, affecting children, adults and families. Genes other than PHOX2B have been found responsible for CCHS in rare cases and there are as yet other unknown genes that may account for the disease. At present, management relies on lifelong ventilatory support and close follow up of dysautonomic progression. BODY: This paper provides a state-of-the-art comprehensive description of CCHS and of the components of diagnostic evaluation and multi-disciplinary management, as well as considerations for future research.

CONCLUSION

Awareness and knowledge of the diagnosis and management of this rare disease should be brought to a large health community including adult physicians and health carers.

Neurodevelopmental outcome and respiratory management of congenital central hypoventilation syndrome: a retrospective study

Background

Congenital central hypoventilation syndrome (CCHS) is a rare disease characterized by sleep apnea. Anoxia often occurs soon after birth, and it is important to prevent anoxia-mediated central nervous system complications; however, data on the relationship between respiratory management and the prognosis for intellectual development of patients with CCHS is not well yet investigate.

Methods

We performed a retrospective chart review cohort study of patients with CCHS in Japan. We investigated the risk and prognostic factors for developmental outcomes and examined the disease in terms of its symptoms, diagnosis, complications, and treatment.

Results

Of the 123 patients with CCHS included in the survey, 88 patients were 6 years old and older. They were divided into two group based on their intelligence quotient. Those treated using positive-pressure ventilation via tracheostomy in the first three months of life had a better developmental prognosis than those managed via tracheostomy after three months of age and those treated by ventilation using mask (OR = 3.80; 95% CI: 1.00–14.37, OR = 4.65; 95% CI: 1.11–19.37). There was no significant difference in physical development (P = 0.64).

Conclusions

The best respiratory treatment for patients with CCHS is ventilation via tracheostomy, initiated ideally before the age of three months.

Novel PHOX2B mutations in congenital central hypoventilation syndrome

BACKGROUND

Congenital central hypoventilation syndrome (CCHS) is caused by mutation of paird-like homeobox 2B (PHOX2B). Approximately 90% of patients were found to carry polyalanine repeat expansion mutation (PARM), and the remaining 10% had non-PARM (NPARM). In PARM, the length of the polyalanine expansion correlates with clinical disease severity. Most patients with NPARM have hypoventilation symptoms in the neonatal period and complications of Hirschsprung disease, dysregulation of autonomic nervous system, and tumors of neural crest origin. Data on the genotype-phenotype association may contribute to the clinical management of the disease.

METHODS

We studied the genetic background of Japanese CCHS patients according to PHOX2B sequencing.

RESULTS

Of 133 Japanese CCHS patients we identified 12 patients carrying 11 different NPARM (approx. 9% of the patients) and described the clinical manifestations in seven of them with the following novel mutations: c.941-945del5, c.678_693dup16, c.609_616del8, c.620_633del14, c.663_711del 49, c.448C>G and c.944G>C. All patients had hypoventilation in the neonatal period and also had Hirschsprung disease, with the exception of two patients carrying c.620_633del14 and c.663_711del49 mutations. The patient carrying the c.609_616del8 mutation also had a benign mediastinal tumor.

CONCLUSION

Most patients carrying NPARM had severe symptoms with frequent complications, as in previous reports, and should be carefully monitored for various complications, including neural crest-derived tumor.

Neonatal Congenital Central Hypoventilation Syndrome: Why We Should not Sleep on it. Literature Review of Forty-two Neonatal Onset Cases

Congenital Central Hypoventilation Syndrome (CCHS), also referred with the expression "Ondine's Curse", is a rare genetic life-long disease resulting from the mutation of PHOX2B gene on chromosome 4p12.3. CCHS represents an autonomic nervous system disorder; its more fearsome manifestation is central hypoventilation, due to a deficient response of chemoreceptors to hypercapnia and hypoxia. Several associated symptoms can occur, such as pupillary anomalies, arrhythmias, reduced heart rate variability, esophageal dysmotility, and structural comorbidities (Hirschsprung's Disease or neural crest tumours). CCHS typical onset is during the neonatal period, but cases of delayed diagnosis have been reported; moreover, both sporadic or familial cases can occur. In preterm newborns, asphyxia and typical prematurity-related findings may overlap CCHS clinical manifestations and make it harder to formulate a correct diagnosis. The early recognition of CCHS allows appropriate management, useful to reduce immediate and long- term consequences.

The genetics of congenital central hypoventilation syndrome: clinical implications

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder of the autonomic nervous system (ANS) and respiratory control. This disorder, formerly referred to as Ondine’s curse, is due to a mutation in the PHOX2B gene that affects the development of the neural crest cells. CCHS has an autosomal dominant pattern of inheritance. Majority of the patients have a polyalanine repeat mutation (PARM) of the PHOX2B, while a small group has non-PARM (NPARM). Knowledge of the patient’s PHOX2B gene mutation helps predict a patient’s clinical presentation and outcome and aids in anticipatory management of the respiratory and ANS dysfunction.

Congenital central hypoventilation syndrome: Broader cognitive deficits revealed by parent controls

OBJECTIVE

To investigate neurocognitive deficits in children with Congenital Central Hypoventilation Syndrome (CCHS) by comparing them to their parents, since parents comprise a particularly suitable control group matched on disease-extrinsic factors that can influence neurocognitive functioning. We compared CCHS patients to their parents and to population norms, hypothesizing that they would obtain lower intelligence test scores than both groups. We also compared patient-parent differences against patient-normative differences, to determine whether the two analytic approaches would yield different results.

METHODS

We administered an intelligence screening, the Shipley-2, to 21 school-aged patients (age 14.2 ± 5.5 years) with PHOX2B mutation-confirmed CCHS and their parents. Patients also received detailed clinical intellectual assessments using the Wechsler scales.

RESULTS

CCHS patients scored significantly below parents on Shipley-2 indices of intelligence, vocabulary, and abstraction, with a trend for perceptual reasoning. The CCHS patients scored significantly below population norms on indices of abstraction and perceptual reasoning. Patient-parent differences were significantly larger than patient-normative differences for vocabulary scores. CCHS patients scored significantly below population norms on Wechsler indices of intelligence, perceptual reasoning, working memory, and processing speed.

CONCLUSIONS

CCHS may affect a broader range of cognitive abilities than previous research based on comparisons to population norms has indicated. Comparisons of CCHS children to their parents reveal deficits of vocabulary and abstract reasoning which have not been previously identified. A full understanding of the neurocognitive impact of CCHS requires comparisons between patients and other individuals such as friends, parents, or siblings who closely resemble them on disease-extrinsic characteristics.

Congenital central hypoventilation syndrome mimicking mitochondrial disease

Later-onset congenital central hypoventilation syndrome (LO-CCHS) does not present only breathing problems but can be present as episodic multiple organs involvement. Our unique case demonstrated LO-CCHS should be considered in the differential diagnosis of mitochondrial diseases and having nontypical polysomnography result.

Congenital central hypoventilation syndrome: a bedside-to-bench success story for advancing early diagnosis and treatment and improved survival and quality of life

The "bedside-to-bench" Congenital Central Hypoventilation Syndrome (CCHS) research journey has led to increased phenotypic-genotypic knowledge regarding autonomic nervous system (ANS) regulation, and improved clinical outcomes. CCHS is a neurocristopathy characterized by hypoventilation and ANS dysregulation. Initially described in 1970, timely diagnosis and treatment remained problematic until the first large cohort report (1992), delineating clinical presentation and treatment options. A central role of ANS dysregulation (2001) emerged, precipitating evaluation of genes critical to ANS development, and subsequent 2003 identification of Paired-Like Homeobox 2B (PHOX2B) as the disease-defining gene for CCHS. This breakthrough engendered clinical genetic testing, making diagnosis exact and early tracheostomy/artificial ventilation feasible. PHOX2B genotype-CCHS phenotype relationships were elucidated, informing early recognition and timely treatment for phenotypic manifestations including Hirschsprung disease, prolonged sinus pauses, and neural crest tumors. Simultaneously, cellular models of CCHS-causing PHOX2B mutations were developed to delineate molecular mechanisms. In addition to new insights regarding genetics and neurobiology of autonomic control overall, new knowledge gained has enabled physicians to anticipate and delineate the full clinical CCHS phenotype and initiate timely effective management. In summary, from an initial guarantee of early mortality or severe neurologic morbidity in survivors, CCHS children can now be diagnosed early and managed effectively, achieving dramatically improved quality of life as adults.

Hirschsprung's disease: clinical dysmorphology, genes, micro-RNAs, and future perspectives

On the occasion of the 100th anniversary of Dr. Harald Hirschsprung's death, there is a worldwide significant research effort toward identifying and understanding the role of genes and biochemical pathways involved in the pathogenesis as well as the use of new therapies for the disease harboring his name (Hirschsprung disease, HSCR). HSCR (aganglionic megacolon) is a frequent diagnostic and clinical challenge in perinatology and pediatric surgery, and a major cause of neonatal intestinal obstruction. HSCR is characterized by the absence of ganglia of the enteric nervous system, mostly in the distal gastrointestinal tract. This review focuses on current understanding of genes and pathways associated with HSCR and summarizes recent knowledge related to micro RNAs (miRNAs) and HSCR pathogenesis. While commonly sporadic, Mendelian patterns of inheritance have been described in syndromic cases with HSCR. Although only half of the patients with HSCR have mutations in specific genes related to early embryonic development, recent pathway-based analysis suggests that gene modules with common functions may be associated with HSCR in different populations. This comprehensive profile of functional gene modules may serve as a useful resource for future developmental, biochemical, and genetic studies providing insights into the complex nature of HSCR.

Congenital central hypoventilation syndrome: diagnostic and management challenges

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder with failure of central control of breathing and of the autonomic nervous system function due to a mutation in the paired-like homeobox 2B (PHOX2B) gene. Affected patients have absent or negligible ventilatory sensitivity to hypercapnia and hypoxemia, and they do not exhibit signs of respiratory distress when challenged with hypercarbia or hypoxia. The diagnosis of CCHS must be confirmed with PHOX2B gene mutation. Generally, the PHOX2B mutation genotype can aid in anticipating the severity of the phenotype. They require ventilatory support for life. Home assisted ventilation options include positive pressure ventilation via tracheostomy, noninvasive positive pressure ventilation, and diaphragm pacing via phrenic nerve stimulation, but each strategy has its associated limitations and challenges. Since all the clinical manifestations of CCHS may not manifest at birth, periodic monitoring and early intervention are necessary to prevent complications and improve outcome. Life-threatening arrhythmias can manifest at different ages and a normal cardiac monitoring study does not exclude future occurrences leading to the dilemma of timing and frequency of cardiac rhythm monitoring and treatment. Given the rare incidence of CCHS, most health care professionals are not experienced with managing CCHS patients, particularly those with diaphragm pacers. With early diagnosis and advances in home mechanical ventilation and monitoring strategies, many CCHS children are surviving into adulthood presenting new challenges in their care.

Significant phenotype variability of congenital central hypoventilation syndrome in a family with polyalanine expansion mutation of the PHOX2B gene

BACKGROUND

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder resulting from mutations in the PHOX2B gene located on chromosome 4p12.3, characterized by hypoventilation secondary to missing responses to both hypercapnia and hypoxia.

CASE REPORT

Proband. A girl, hospitalised 5 times for respiratory failure from 6 weeks old, presented at 4 years of age severe cyanosis related to pneumonia. Tracheostomy was done, and she was discharged home using a portable positive pressure ventilator during sleep. Proband's father: The father was retrospectively found out to suffer from severe headache and excessive daytime sleepiness. Molecular genetic evaluation of PHOX2B gene was performed and casual polyalanine repeat expansion mutation c.741_755dup15 in exon 3 was found both in proband and her father in heterozygous form. The proband's grandmother died of respiratory failure after administration of benzodiazepine at the age of fifty years. Considering the grandmother's history, she is highly suspected of having had CCHS as well.

CONCLUSION

Repeated respiratory failure of girl was explained by PHOX2B mutation and Ondina curse. Proband´s father has incompletely penetrated PHOX2B heterozygous mutation as well and proband´s grandmother died probably from the consequences of drug interaction with PHOX2B mutated background as well. Both daughter and father currently require overnight mechanical ventilatory support. Although most PHOX2B mutations occur de novo, our case is a rare three generation family affected by autosomal dominant inheritance with incomplete penetrance manifested as the late-form of CCHS and proven PHOX2B mutation in two generations.

Next-generation sequencing-based molecular diagnosis of neonatal hypotonia in Chinese Population

Neonatal hypotonia is extremely challenging to diagnose because numerous disorders present similar clinical manifestations. Two panels for diagnosing neonatal hypotonia were developed, which enriches 35 genes corresponding to 61 neonatal hypotonia-related disorders. A cohort of 214 neonates with hypotonia was recruited from 2012 to 2014 in China for this study. Of these subjects, twenty-eight neonates with hypotonia were eliminated according to exclusion criteria and 97 were confirmed using traditional detection methods. The clinical diagnoses of the remaining 89 neonates with hypotonia were approached by targeted next-generation sequencing (NGS). Among the 89 tested neonates, 25 potentially pathogenic variants in nine genes (RYR1, MECP2, MUT, CDKL5, MPZ, PMM2, MTM1, LAMA2 and DMPK) were identified in 22 patients. Six of these pathogenic variants were novel. Of the 186 neonates with hypotonia, we identified the genetic causes for 117 neonates by the traditional detection methods and targeted NGS, achieving a high solving rate of 62.9%. In addition, we found seven neonates with RETT syndrome carrying five mutations, thus expanding the mutation profiles in Chinese neonates with hypotonia. Our study highlights the utility of comprehensive molecular genetic testing, which provides the advantage of speed and diagnostic specificity without invasive procedures.