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conducted a narrative review of literature on neurocognitive outcomes in CCHS and ROHHAD, supplemented with previously unpublished data from patients with CCHS and ROHHAD at our Center for Autonomic Medicine in Pediatrics (CAMP).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

Mutations in MYO1H cause a recessive form of central hypoventilation with autonomic dysfunction.

BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is a rare life-threatening disorder of respiratory and autonomic regulation. It is classically caused by dominant mutations in the transcription factor PHOX2B. The objective of the present study was to identify the molecular cause of a recessive form of central hypoventilation with autonomic dysfunction. METHODS: Here, we used homozygosity mapping and whole-genome sequencing in a consanguineous family with CCHS in combination with functional analyses in CRISPR/Cas9 engineered mice. RESULTS: We report on a consanguineous family with three affected children, all tested PHOX2B mutation negative, presenting with alveolar hypoventilation and symptoms of autonomic dysregulation. Whole-genome sequencing revealed a homozygous frameshift mutation in exon 25 of the MYO1H gene (c.2524_2524delA) segregating with the phenotype in the family. MYO1H encodes for the unconventional myosin IH, which is thought to function as a motor protein in intracellular transport and vesicle trafficking. We show that Myo1h is broadly expressed in the mouse lower medulla, including the CO2-sensitive Phox2b+ retrotrapezoid neurons. To test the pathogenicity of the variant, we engineered two Myo1h mutant mouse strains: the first strain (Myo1h*) resembling the human mutation and the second being a full knock-out (Myo1hFS ). Whole-body plethysmography studies in Myo1h* newborns with the re-engineered human mutation revealed hypoventilation and a blunted response to CO2, recapitulating the breathing phenotype observed in the kindred. CONCLUSIONS: Our results identify MYO1H as an important gene in CO2 sensitivity and respiratory control and as the cause of a rare recessive form of congenital central hypoventilation.

Recurrence of CCHS-associated PHOX2B Poly-Alanine expansion variant due to paternal mosaicism.

BACKGROUND: Paired-like Homeobox 2B (PHOX2B) is considered the causative gene of Congenital Central Hypoventilation Syndrome (CCHS), a dominant genetic disorder characterized by impaired central respiratory control and subsequent hypoventilation during sleep. METHODS: Herein, we present a family with recurrent severe CCHS. The potential causative genetic variant was confirmed through Whole-Exome Sequencing (WES), Sanger sequencing, and droplet digital PCR (ddPCR). Furthermore, prenatal diagnosis was performed on the proband's mother at 20 weeks of her fourth pregnancy upon request. RESULTS: The proband and her brother were both carriers of the PHOX2B polyalanine expansion variant: c.744_758dupCGCGGCAGCGGCGGCGGCGGC. Sanger sequencing revealed that the proband's father had a small variant peak in the gene position, implying potential somatic mosaicism. In addition, ddPCR results showed that the proband's father had germline mosaicism, with a mosaicism proportion of 14.3%. Notably, the detect p.(Ala241[26]) variant was not detected in the fetus. CONCLUSIONS: These findings have important implications for improving genetic counseling of CCHS families as they suggest that even parents without CCHS symptoms may have somatic chimerism, necessitating careful genetic counseling and consideration of prenatal testing for subsequent pregnancies.

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.

Case Report: A novel PHOX2B p.Ala248_Ala266dup variant causing congenital central hypoventilation syndrome.

Introduction: Congenital central hypoventilation syndrome (CCHS) is a rare disease characterized by central alveolar hypoventilation and impaired autonomic regulation, caused by pathogenic variants of PHOX2B gene. More than 90% of patients have a polyalanine repeat mutation (PARM) in the heterozygous state, characterized by the expansion of GCN repeats and an increase in the number of alanine repeats, so that genotypes 20/24-20/33 are formed (the normal genotype is 20/20). The remaining 10% of patients harbor non-PARMs. Case description: We present a clinical case of a girl with a novel PHOX2B heterozygous genetic variant in the exon 3: NM_003924.4: c.735_791dup, p.Ala248_Ala266dup. The duplication includes 16 GCN (alanine) repeats and 3 adjacent amino acids. Both clinically healthy parents demonstrated a normal PHOX2B sequence. In addition, the girl has a variant of unknown significance in RYR1 gene and a variant of unknown significance in NKX2-5 gene. The child's phenotype is quite special. She needs ventilation during sleep, and has Hirschsprung's disease type I, arteriovenous malformation S4 of the left lung, ventricular and atrium septal defects, coronary right ventricular fistula, hemodynamically nonsignificant, episodes of sick sinus and atrioventricular dissociation with bradycardia, divergent alternating strabismus, and oculus uterque (both eyes) (OU) retinal angiopathy. Two episodes of hypoglycemic seizures were also registered. Severe pulmonary hypertension resolved after appropriate ventilation adjustment. Diagnostic odyssey was quite dramatic. Conclusion: Detection of a novel PHOX2B variant expands the understanding of molecular mechanisms of CCHS and genotype-phenotype correlations.

Developmental disorders affecting the respiratory system: CCHS and ROHHAD.

Rapid-onset Obesity with Hypothalamic dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD) and Congenital Central Hypoventilation Syndrome (CCHS) are ultra-rare distinct clinical disorders with overlapping symptoms including altered respiratory control and autonomic regulation. Although both disorders have been considered for decades to be on the same spectrum with necessity of artificial ventilation as life-support, recent acquisition of specific knowledge concerning the genetic basis of CCHS coupled with an elusive etiology for ROHHAD have definitely established that the two disorders are different. CCHS is an autosomal dominant neurocristopathy characterized by alveolar hypoventilation resulting in hypoxemia/hypercarbia and features of autonomic nervous system dysregulation (ANSD), with presentation typically in the newborn period. It is caused by paired-like homeobox 2B (PHOX2B) variants, with known genotype-phenotype correlation but pathogenic mechanism(s) are yet unknown. ROHHAD is characterized by rapid weight gain, followed by hypothalamic dysfunction, then hypoventilation followed by ANSD, in seemingly normal children ages 1.5-7 years. Postmortem neuroanatomical studies, thorough clinical characterization, pathophysiological assessment, and extensive genetic inquiry have failed to identify a cause attributable to a traditional genetic basis, somatic mosaicism, epigenetic mechanism, environmental trigger, or other. To find the key to the ROHHAD pathogenesis and to improve its clinical management, in the present chapter, we have carefully compared CCHS and ROHHAD.

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.

Neonatal apneic phenotype in a murine congenital central hypoventilation syndrome model is induced through non-cell autonomous developmental mechanisms.

Congenital central hypoventilation syndrome (CCHS) represents a rare genetic disorder usually caused by mutations in the homeodomain transcription factor PHOX2B. Some CCHS patients suffer mainly from deficiencies in CO2 and/or O2 respiratory chemoreflex, whereas other patients present with full apnea shortly after birth. Our goal was to identify the neuropathological mechanisms of apneic presentations in CCHS. In the developing murine neuroepithelium, Phox2b is expressed in three discrete progenitor domains across the dorsal-ventral axis, with different domains responsible for producing unique autonomic or visceral motor neurons. Restricting the expression of mutant Phox2b to the ventral visceral motor neuron domain induces marked newborn apnea together with a significant loss of visceral motor neurons, RTN ablation, and preBötzinger complex dysfunction. This finding suggests that the observed apnea develops through non-cell autonomous developmental mechanisms. Mutant Phox2b expression in dorsal rhombencephalic neurons did not generate significant respiratory dysfunction, but did result in subtle metabolic thermoregulatory deficiencies. We confirm the expression of a novel murine Phox2b splice variant which shares exons 1 and 2 with the more widely studied Phox2b splice variant, but which differs in exon 3 where most CCHS mutations occur. We also show that mutant Phox2b expression in the visceral motor neuron progenitor domain increases cell proliferation at the expense of visceral motor neuron development. We propose that visceral motor neurons may function as organizers of brainstem respiratory neuron development, and that disruptions in their development result in secondary/non-cell autonomous maldevelopment of key brainstem respiratory neurons.

Management of Rare Causes of Pediatric Chronic Respiratory Failure.

The need for long-term noninvasive positive pressure ventilation (NiPPV) in children with chronic respiratory failure is rapidly growing. This article reviews pediatric-specific considerations of NiPPV therapy. Indications for NiPPV therapy can be categorized by the cause of the respiratory failure: (1) upper airway obstruction, (2) musculoskeletal and/or neuromuscular disease, (3) lower respiratory tract diseases, and (4) control of breathing abnormalities. The role of NiPPV therapy in select rare conditions (spinal muscular atrophy, congenital central hypoventilation syndrome, cerebral palsy, scoliosis, and Chiari malformations) is also reviewed.

Obstructive Sleep Apnea in Patients With Congenital Central Hypoventilation Syndrome Ventilated by Diaphragm Pacing Without Tracheostomy.

STUDY OBJECTIVES: To determine presence of obstructive sleep apnea (OSA) in patients with congenital central hypoventilation syndrome (CCHS) ventilated by diaphragm pacing (DP) without tracheostomy, and to determine if OSA can be improved by DP setting changes. METHODS: We reviewed polysomnography (PSG) results of 15 patients with CCHS from October 2001 to April 2014, age 15.4 ± 7.8 years, body mass index 22.0 ± 6.0 kg/m2, and 60% female. RESULTS: Of the 22 PSG results obtained for the 15 patients with CCHS, 9 were performed with tracheostomy capped, and 13 were performed after patients underwent decannulation. OSA was present on 6 of 9 tests in patients with tracheostomy capped, including 3 patients with immediate, severe OSA necessitating that the studies be completed with tracheostomy uncapped. OSA was present on 2 of 13 tests in patients in whom decannulation had been performed. Hypoventilation was seen on only one test without OSA. On 2 of 5 tests showing OSA, OSA improved by decreasing DP amplitude settings; apnea-hypopnea index decreased from 11.1 ± 2.5 to 1.8 ± 2.5 events/h; PETCO2 decreased from 57.5 ± 3.5 to 38.5 ± 0.7 torr; SpO2 increased from 76.5 ± 0.7% to 93.0 ± 7.1%. OSA improved in one patient with slight increase in respiratory rate. Settings were manipulated in 4 tests showing OSA; no changes were attempted in the remaining study. One patient was placed on bilevel positive airway pressure with temporary suspension of DP. Age (P < .119), previous adenotonsillectomy (P < .211), and body mass index (P < .112) did not significantly contribute to OSA. CONCLUSIONS: OSA occurs in patients with CCHS ventilated by DP. However, decreasing DP amplitude settings can lessen upper airway obstruction without compromising gas exchange.

Novel mutation-deletion in the PHOX2B gene of the patient diagnosed with Neuroblastoma, Hirschsprung's Disease, and Congenital Central Hypoventilation Syndrome (NB-HSCR-CCHS) Cluster.

INTRODUCTION: Neuroblastoma (NB), Hirschsprung disease (HSCR), Congenital Central Hypoventilation Syndrome (CCHS), clinically referred as the NB-HSCR-CCHS cluster, are genetic disorders linked to mutations in the PHOX2B gene on chromosome 4p12. SPECIFIC AIM: The specific aim of this project is to define the PHOX2B gene mutations as the genomic basis for the clinical manifestations of the NB-HSCR-CCHS cluster. PATIENT: A one day old male patient presented to the Jagiellonian University Medical College (JUMC), American Children Hospital, neonatal Intensive Care Unit (ICU) due to abdominal distention, vomiting, and severe apneic episodes. With the preliminary diagnosis of the NB-HSCR-CCHS, the blood and tissue samples were acquired from the child, as well as from the child's parents. All procedures were pursued in accordance with the Declaration of Helsinki, with the patient's Guardian Informed Consent and the approval from the Institutional Review Board. GENETIC/GENOMIC METHODS: Karyotyping was analyzed based upon Giemsa banding. The patient's genomic DNA was extracted from peripheral blood and amplified by polymerase chain reaction. Direct microfluidic Sanger sequencing was performed on the genomic DNA amplicons. These procedures were pursued in addition to the routine clinical examinations and tests. RESULTS: G-banding showed the normal 46 XY karyotype. However, genomic sequencing revealed a novel, heterozygous deletion (8 nucleotides: c.699-706, del8) in exon 3 of the PHOX2B gene on chromosome 4. This led to the frame-shift mutation and malfunctioning gene expression product. CONCLUSION: Herein, we report a novel PHOX2B gene mutation in the patient diagnosed with the NB-HSCR-CCHS cluster. The resulting gene expression product may be a contributor to the clinical manifestations of these genetic disorders. It adds to the library of the mutations linked to this syndrome. Consequently, we suggest that screening for the PHOX2B mutations becomes an integral part of genetic counseling, genomic sequencing of fetal circulating nucleic acids and / or genomes of circulating fetal cells prenatally, while preparing supportive therapy upon delivery, as well as on neonates' genomes of intubated infants, when breathing difficulties occur upon extubation. Further, we hypothesize that PHOX2B may be considered as a potential target for gene therapy.

A case of congenital central hypoventilation syndrome with a novel mutation of the PHOX2B gene presenting as central sleep apnea.

UNLABELLED: Congenital central hypoventilation syndrome (CCHS) is a rare disease characterized by abnormal autonomic control of breathing resulting in hypoventilation. We report an infant girl with CCHS who presented with central sleep apnea, which was first demonstrated by polysomnography when the infant was 5 months old. She was heterozygous for the novel 590delG mutation of PHOX2B, which is classified as a non-polyalanine repeat mutation (NPARM). This mutation is considered to be associated with a relatively mild phenotype. CITATION: Amimoto Y; Okada K; Nakano H; Sasaki A; Hayasaka K; Odajima H. A case of congenital central hypoventilation syndrome with a novel mutation of the PHOX2B gene presenting as central sleep apnea.

Recurrence of CCHS associated PHOX2B poly-alanine expansion mutation due to maternal mosaicism.

Heterozygous in frame trinucleotide duplications within the PHOX2B gene, leading to poly-alanine expansions, cause Congenital Central Hypoventilation Syndrome. Here we report about a CCHS patient, carrying a +13Ala PHOX2B expansion, whose asymptomatic mother resulted with a low level of mosaicism for the same mutation in peripheral blood cells. Her second pregnancy ended with the spontaneous miscarriage of a fetus who had inherited the PHOX2B mutation, thus confirming germline mosaicism in the mother and the need of proper genetic counseling to CCHS families.