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

[Two children with late-onset congenital central hypoventilation syndrome]

Two children with late-onset congenital central hypoventilation syndrome were reported, one of whom was male and had no abnormal manifestations after birth, respiratory failure occurs at the age of 1 year and 6 months. After being hospitalized, he was treated with oxygen inhalation and non-invasive ventilation, but carbon dioxide retention could not be corrected. After one month of tracheal intubation, he was failure to wean from ventilator, so tracheostomy was performed. He needs a ventilator to help breath while sleeping, and can breath autonomously during the day without ventilator. The other case was a female, with no abnormalities after birth. At the age of 11 months, she developed respiratory failure. During sleep, the child needs non-invasive assisted ventilation through a nasal mask, and during the day, she breathed autonomously.Two patients were followed up forever 2 years and their growth and development were normal.

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.

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.

NH2-terminal deletion of specific phosphorylation sites on PHOX2B disrupts the formation of enteric neurons in vivo

Mutations in the paired-like homeobox 2 b (PHOX2B) gene are associated with congenital central hypoventilation syndrome (CCHS), which is a rare condition in which both autonomic dysregulation with hypoventilation and an enteric neuropathy may occur. The majority of patients with CCHS have a polyalanine repeat mutation (PARM) in PHOX2B, but a minority of patients have nonpolyalanine repeat mutations (NPARMs), some of which have been localized to exon 1. A PHOX2B-Y14X nonsense mutation previously generated in a human pluripotent stem cell (hPSC) line results in an NH₂-terminus truncated product missing the first 17 or 20 amino acids, possibly due to translational reinitiation at an alternate ATG start site. This NH₂-terminal truncation in the PHOX2B protein results in the loss of two key phosphorylation residues. Though the deletion does not affect the potential for PHOX2B^Y14X/Y14X mutant hPSC to differentiate into enteric neural crest cells (ENCCs) in culture, it impedes in vivo development of neurons in an in vivo model of human aganglionic small intestine.NEW & NOTEWORTHY A mutation that affects only 17-20 NH₂-terminal amino acids in the paired-like homeobox 2 b (PHOX2B) gene hinders the subsequent in vivo establishment of intestinal neuronal cells, but not the in vitro differentiation of these cells.

Reduced PHOX2B stability causes axonal growth impairment in motor neurons with TARDBP mutations

Amyotrophic lateral sclerosis (ALS) is an adult-onset incurable motor neuron (MN) disease. The reasons for selective MN vulnerability in ALS are unknown. Axonal pathology is among the earliest signs of ALS. We searched for novel modulatory genes in human MN axon shortening affected by TARDBP mutations. In transcriptome analysis of RNA present in the axon compartment of human-derived induced pluripotent stem cell (iPSC)-derived MNs, PHOX2B (paired-like homeobox protein 2B) showed lower expression in TARDBP mutant axons, which was consistent with axon qPCR and in situ hybridization. PHOX2B mRNA stability was reduced in TARDBP mutant MNs. Furthermore, PHOX2B knockdown reduced neurite length in human MNs. Finally, phox2b knockdown in zebrafish induced short spinal axons and impaired escape response. PHOX2B is known to be highly express in other types of neurons maintained after ALS progression. Collectively, TARDBP mutations induced loss of axonal resilience, which is an important ALS-related phenotype mediated by PHOX2B downregulation.

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Human iPSCs were established from a familial ALS with the TARDBP p.G376D mutation

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PHOX2B mRNA was identified to be decreased in TARDBP mutant MNs by RNA sequencing

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PHOX2B mRNA bind to TDP-43 and its stability was reduced in TARDBP mutant MNs

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PHOX2B knockdown reduced neurite length and impaired motor functions in vivo/vitro

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

STUDY OBJECTIVES

Congenital central hypoventilation syndrome (CCHS) is a rare disorder affecting the autonomic nervous system that is caused by variants in the PHOX2B gene. About 10% of patients with CCHS have nonpolyalanine repeat mutations (NPARM) that are associated with severe phenotypes requiring continuous assisted ventilation, Hirschsprung's disease, and increased neural crest tumor risk. However, some patients with NPARMs have milder phenotypes. Our objective was to describe the phenotypes in patients with CCHS PHOX2B NPARM.

METHODS

Retrospective case series of patients with CCHS PHOX2B NPARM was conducted at two children's hospitals to evaluate their phenotypes.

RESULTS

We identified eight patients with CCHS PHOX2B NPARM aged 3-31 years. Seven patients were diagnosed in infancy and one patient at two years of age. All patients presented with respiratory depression in the first two months of life. Only one patient was identified with a severe phenotype requiring continuous assisted ventilation, Hirschsprung's disease, and a neural crest tumor, that was resected. Five patients required positive pressure ventilation via tracheostomy only during sleep and two patients required oxygen only during sleep. Four patients had Hirschsprung's disease and one patient had a cardiac pacemaker due to a bradyarrhythmia. None of the patients had echocardiographic abnormalities.

CONCLUSIONS

Patients with CCHS PHOX2B NPARM can have variable phenotypes emphasizing the importance of implementing a plan of care that is individualized for each patient. The type of NPARM and its respective location on the PHOX2B gene may play a critical role in the severity of phenotypes displayed by each patient.

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

PURPOSE

CCHS is an extremely rare congenital disorder requiring artificial ventilation as life support. Typically caused by heterozygous polyalanine repeat expansion mutations (PARMs) in the PHOX2B gene, identification of a relationship between PARM length and phenotype severity has enabled anticipatory management. However, for patients with non-PARMs in PHOX2B (NPARMs, ~10% of CCHS patients), a genotype-phenotype correlation has not been established. This comprehensive report of PHOX2B NPARMs and associated phenotypes, aims at elucidating potential genotype-phenotype correlations that will guide anticipatory management.

METHODS

An international collaboration (clinical, commercial, and research laboratories) was established to collect/share information on novel and previously published PHOX2B NPARM cases. Variants were categorized by type and gene location. Categorical data were analyzed with chi-square and Fisher's exact test; further pairwise comparisons were made on significant results.

RESULTS

Three hundred two individuals with PHOX2B NPARMs were identified, including 139 previously unreported cases. Findings demonstrate significant associations between key phenotypic manifestations of CCHS and variant type, location, and predicted effect on protein function.

CONCLUSION

This study presents the largest cohort of PHOX2B NPARMs and associated phenotype data to date, enabling genotype-phenotype studies that will advance personalized, anticipatory management and help elucidate pathological mechanisms. Further characterization of PHOX2B NPARMs demands longitudinal clinical follow-up through international registries.

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.

A respiratory/Hirschsprung phenotype in a three-generation family associated with a novel pathogenic PHOX2B splice donor mutation

BACKGROUND

Mutations in the PHOX2B gene cause congenital central hypoventilation syndrome (CCHS), a rare autonomic nervous system dysfunction disorder characterized by a decreased ventilatory response to hypercapnia. Affected subjects develop alveolar hypoventilation requiring ventilatory support particularly during the non-REM phase of sleep. In more severe cases, hypoventilation may extend into wakefulness. CCHS is associated with disorders characterized by the defective migration/differentiation of neural crest derivatives, including aganglionic megacolon or milder gastrointestinal phenotypes, such as constipation. Most cases of CCHS are de novo, caused by heterozygosity for polyalanine repeat expansion mutations (PARMs) in exon 3. About 10% of cases are due to heterozygous non-PARM missense, nonsense or frameshift mutations.

METHODS

We describe a three-generation Maltese-Caucasian family with a variable respiratory/Hirschsprung phenotype, characterized by chronic constipation, three siblings with Hirschsprung disease necessitating surgery, chronic hypoxia, and alveolar hypoventilation requiring non-invasive ventilation.

RESULTS

The sequencing of PHOX2B revealed a novel heterozygous c.241+2delT splice variant in exon 1 that segregates with the CCHS/Hirschsprung phenotype in the family. The mutation generates a non-functional splice site with a deleterious effect on protein structure and is pathogenic according to ACMG P VS1, PM2, and PP1 criteria.

CONCLUSION

This report is significant as no PHOX2B splice-site mutations have been reported. Additionally, it highlights the variability in clinical expression and disease severity of non-PARM mutations.

A purely quantitative form of partial recessive IFN-γR2 deficiency caused by mutations of the initiation or second codon

Mendelian susceptibility to mycobacterial disease (MSMD) is characterized by clinical disease caused by weakly virulent mycobacteria, such as environmental mycobacteria and Bacillus Calmette-Guérin vaccines, in otherwise healthy individuals. All known genetic etiologies disrupt interferon (IFN)-γ immunity. Germline bi-allelic mutations of IFNGR2 can underlie partial or complete forms of IFN-γ receptor 2 (IFN-γR2) deficiency. Patients with partial IFN-γR2 deficiency express a dysfunctional molecule on the cell surface. We studied three patients with MSMD from two unrelated kindreds from Turkey (P1, P2) and India (P3), by whole-exome sequencing. P1 and P2 are homozygous for a mutation of the initiation codon(c.1A>G) of IFNGR2, whereas P3 is homozygous for a mutation of the second codon (c.4delC). Overexpressed mutant alleles produce small amounts of full-length IFN-γR2 resulting in an impaired, but not abolished, response to IFN-γ. Moreover, SV40-fibroblasts of P1 and P2 responded weakly to IFN-γ, and Epstein Barr virus-transformed B cells had a barely detectable response to IFN-γ. Studies in patients' primary T cells and monocyte-derived macrophages yielded similar results. The residual expression of IFN-γR2 protein of normal molecular weight and function is due to the initiation of translation between the second and ninth non-AUG codons. We thus describe mutations of the first and second codons of IFNGR2, which define a new form of partial recessive IFN-γR2 deficiency. Residual levels of IFN-γ signaling were very low, accounting for the more severe clinical phenotype of these patients with residual expression levels of normally functional surface receptors than of patients with partial recessive IFN-γR2 deficiency due to surface-expressed dysfunctional receptors, whose residual levels of IFN-γ signaling were higher.

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.

Characterization of a recurrent missense mutation in the forkhead DNA-binding domain of FOXP1

Haploinsufficiency of Forkhead box protein P1 (FOXP1), a highly conserved transcription factor, leads to developmental delay, intellectual disability, autism spectrum disorder, speech delay, and dysmorphic features. Most of the reported FOXP1 mutations occur on the C-terminus of the protein and cluster around to the forkhead domain. All reported FOXP1 pathogenic variants result in abnormal cellular localization and loss of transcriptional repression activity of the protein product. Here we present three patients with the same FOXP1 mutation, c.1574G>A (p.R525Q), that results in the characteristic loss of transcription repression activity. This mutation, however, represents the first reported FOXP1 mutation that does not result in cytoplasmic or nuclear aggregation of the protein but maintains normal nuclear localization.

Atypical presentations associated with non-polyalanine repeat PHOX2B mutations

Congenital central hypoventilation syndrome (CCHS) is a disorder of ventilatory control and autonomic dysregulation that can be caused by mutations in the paired-like homeobox 2B (PHOX2B) gene. The majority of CCHS cases are caused by polyalanine repeat mutations (PARMs) in PHOX2B; however, in rare cases, non-polyalanine repeat mutations (NPARMs) have been identified. Here, we report two patients with NPARMs in PHOX2B. Patient 1 has a mild CCHS phenotype seen only on polysomnogram, which was performed for desaturations and stridor following a bronchiolitis episode, and characterized by night-time hypoventilation and a history of ganglioneuroblastoma. She carried a novel de novo missense variant, p.R102S (c.304C > A), in exon 2. Patient 2 has an atypical CCHS phenotype including micrognathia, gastroesophageal reflux, stridor, hypopnea, and intermittent desaturations. Sleep study demonstrated that Patient 2 had daytime and night-time hypercarbia with obstructive sleep apnea, requiring tracheostomy. On PHOX2B sequencing, she carried a recently identified nonsense variant, p.Y78* (c.234C > G), in exon 1. In summary, we present two patients with CCHS and identified NPARMs in PHOX2B who have distinct differences in phenotype severity, further elucidating the range of clinical outcomes in CCHS and illustrating the necessity of considering PHOX2B mutations when encountering atypical CCHS presentations.

Expanding the phenotype of congenital central hypoventilation syndrome impacts management decisions

Congenital central hypoventilation syndrome (CCHS) is a neurocristopathy caused by pathogenic heterozygous variants in the gene paired-like homeobox 2b (PHOX2B). It is characterized by severe infantile alveolar hypoventilation. Individuals may also have diffuse autonomic nervous system dysfunction, Hirschsprung disease and neural crest tumors. We report three individuals with CCHS due to an 8-base pair duplication in PHOX2B; c.691_698dupGGCCCGGG (p.Gly234Alafs*78) with a predominant enteral and neural crest phenotype and a relatively mild respiratory phenotype. The attenuated respiratory phenotype reported here and elsewhere suggests an emergent genotype:phenotype correlation which challenges the current paradigm of invoking mechanical ventilation for all infants diagnosed with CCHS. Best treatment requires careful clinical judgment and ideally the assistance of a care team with expertise in CCHS.

Genotype-phenotype investigation of 35 patients from 11 unrelated families with camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome

Background

The camptodactyly–arthropathy–coxa vara–pericarditis syndrome (CACP) is a rare autosomal recessive condition characterized by camptodactyly, noninflammatory arthropathy, coxa vara, and pericarditis. CACP is caused by mutations in the proteoglycan 4 (PRG4) gene, which encodes a lubricating glycoprotein present in the synovial fluid and at the surface of articular cartilage.

Methods

In the present study, we compared the clinical and molecular findings of CACP syndrome in 35 patients from 11 unrelated families. In 28 patients, whole exome sequencing was used to investigate genomic variations.

Results

We found that camptodactyly of hands was the first symptom presented by most patients. Swelling of wrists, knees, and elbows began before 4 years of age, while the age of joint involvement was variable. Patients reported an increased pain level after the age of 10, and severe hip involvement developed after 20 years old. All patients presented developmental coxa vara and seven patients (~22%) had pleural effusion, pericarditis, and/or ascites. We identified nine novel genomic alterations, including the first case of homozygous complete deletion of exon 1 in the PRG4 gene.

Conclusion

With this study, we contribute to the catalog of CACP causing variants. We confirm that the skeletal component of this disease worsens with age, and presents the potential mechanisms for interfamily variability, by discussing the influence of a modifier gene and escape from nonsense‐mediated mRNA decay. We believe that this report will increase awareness of this familial arthropathic condition and the characteristic clinical and radiological findings will facilitate the differentiation from the common childhood rheumatic diseases such as juvenile idiopathic arthritis.

Loss of αB-crystallin function in zebrafish reveals critical roles in the development of the lens and stress resistance of the heart

Genetic mutations in the human small heat shock protein αB-crystallin have been implicated in autosomal cataracts and skeletal myopathies, including heart muscle diseases (cardiomyopathy). Although these mutations lead to modulation of their chaperone activity in vitro, the in vivo functions of αB-crystallin in the maintenance of both lens transparency and muscle integrity remain unclear. This lack of information has hindered a mechanistic understanding of these diseases. To better define the functional roles of αB-crystallin, we generated loss-of-function zebrafish mutant lines by utilizing the CRISPR/Cas9 system to specifically disrupt the two αB-crystallin genes, αBa and αBb We observed lens abnormalities in the mutant lines of both genes, and the penetrance of the lens phenotype was higher in αBa than αBb mutants. This finding is in contrast with the lack of a phenotype previously reported in αB-crystallin knock-out mice and suggests that the elevated chaperone activity of the two zebrafish orthologs is critical for lens development. Besides its key role in the lens, we uncovered another critical role for αB-crystallin in providing stress tolerance to the heart. The αB-crystallin mutants exhibited hypersusceptibility to develop pericardial edema when challenged by crowding stress or exposed to elevated cortisol stress, both of which activate glucocorticoid receptor signaling. Our work illuminates the involvement of αB-crystallin in stress tolerance of the heart presumably through the proteostasis network and reinforces the critical role of the chaperone activity of αB-crystallin in the maintenance of lens transparency.

Carbamazepine Improves Apneic Episodes in Congenital Central Hypoventilation Syndrome (CCHS) With a Novel PHOX2B Exon 1 Missense Mutation

ABSTRACT

Pathogenic variants in Paired-Like Homeobox 2B (PHOX2B) gene cause congenital central hypoventilation syndrome (CCHS), a rare disorder of the nervous system characterized by absent or reduced ventilatory response to hypoxia and hypercapnia. The focus of management in CCHS is optimizing ventilation. Thus far, no medication has proved effective in improving ventilation. Most CCHS cases are caused by polyalanine repeat expansion mutations. Non-polyalanine repeat expansion mutations are the cause in 8% of cases and result in a more severe clinical presentation. PHOX2B has 3 exons. Exon 3 of PHOX2B is the most common location for CCHS-causing mutations. Thus far, only 9 CCHS-causing mutations have been reported in exon 1, 8 of which were nonsense mutations. We report a child with CCHS who was found to have a novel heterozygous missense variant in exon 1; c.95A > T. Improvement in his apneic episodes was observed following treatment with carbamazepine.

Congenital central hypoventilation syndrome: An overview of etiopathogenesis, associated pathologies, clinical presentation, and management

Congenital central hypoventilation syndrome (CCHS), known colloquially as Ondine's curse, is a rare disorder characterized by impaired autonomic control of breathing during sleep from the loss of vagal input and diminished sensitivity of CO₂ receptors in the medulla. CCHS correlates to the malformation of the neural crest located in the brainstem; this consequently affects the loss of sensitivity of CO₂ chemoreceptors, bringing about hypoventilation during sleep. The primary cause of CCHS is the mutation of the paired-like homeobox PHO2XB gene, found in 90% of the patients. This mutation not only affects breathing but also drives neurological abnormalities such as autonomic and neurocognitive dysfunction. Though typically congenital, there have been late-onset (i.e., acquired) cases reported. It is vital for physicians and clinicians to be able to diagnose CCHS due to its similar presentation to other syndromes and disorders, which may cause it to be misdiagnosed and may account for its deleterious effects. CCHS can lead to a constellation of symptoms, and consideration of diseases that present concomitantly with CCHS affords us a better understanding of the etiology of this illness. Although a rare syndrome, we aim to review the current literature to emphasize the pathogenesis, etiology, clinical presentation, symptoms, diagnosis, and current treatment methods of CCHS for clinicians to better identify and understand this condition.