Late-onset, insidious course and invasive treatment of congenital central hypoventilation syndrome in a case with the Phox2B mutation: case report

Adult-onset congenital central hypoventilation syndrome due to PHOX2B mutation

Central hypoventilation in adult patients is a rare life-threatening condition characterised by the loss of automatic breathing, more pronounced during sleep. In most cases, it is secondary to a brainstem lesion or to a primary pulmonary, cardiac or neuromuscular disease. More rarely, it can be a manifestation of congenital central hypoventilation syndrome (CCHS). We here describe a 25-year-old woman with severe central hypoventilation triggered by analgesics. Genetic analysis confirmed the diagnosis of adult-onset CCHS caused by a heterozygous de novo poly-alanine repeat expansion of the PHOX2B gene. She was treated with nocturnal non-invasive ventilation. We reviewed the literature and found 21 genetically confirmed adult-onset CCHS cases. Because of the risk of deleterious respiratory complications, adult-onset CCHS is an important differential diagnosis in patients with central hypoventilation.

Adult cases of late-onset congenital central hypoventilation syndrome and paired-like homeobox 2B-mutation carriers: an additional case report and pooled analysis

STUDY OBJECTIVES

Congenital central hypoventilation syndrome (CCHS) is caused by the paired-like homeobox 2B (PHOX2B) mutation and predominantly diagnosed during the neonatal period. Although late-onset CCHS and PHOX2B mutation carriers have been reported, the features of these disease states in adults remain uncertain. This study aimed to identify the characteristics of adult-onset CCHS and PHOX2B-mutation carriers in adult.

METHODS

We mainly searched the PubMed/Medline and Cochrane Databases and classified our target patients into 2 groups: group A, symptomatically diagnosed with late-onset CCHS in adulthood; group B, adult PHOX2B-mutation carriers. Then, clinical characteristics, including the onset, treatment, long-term course, and pattern of the PHOX2B mutation in both groups were analyzed. Additionally, a new adult-case of late-onset CCHS was added to the analysis.

RESULTS

Group A was comprised of 12 patients. The onset triggers of illness included a history of respiratory compromise following general anesthesia and respiratory tract infections. All patients in group A had 20/25 polyalanine repeat mutations and required some chronic ventilatory support at least during sleep, including portable positive pressure ventilator via tracheostomy or noninvasive positive pressure ventilation. In these patients with ventilatory support during sleep, sudden death or poor prognosis was not reported. Group B was comprised of 33 adults from 24 families with PHOX2B mutations. Nine patients in group B were confirmed with the diagnosis of CCHS. Although polyalanine repeat mutations 20/25 represented the most common gene mutation, diverse mutations, including mosaicism, were observed. Hypoventilation of several cases in group B were underdiagnosed by overnight polysomnography without monitoring for CO₂.

CONCLUSION

Alveolar hypoventilation with unknown origin can be caused by the PHOX2B mutation even in adult cases. Both the identification of the PHOX2B mutation and the incorporation of capnography in polysomnography are important for adult cases with unexplained alveolar hypoventilation or asymptomatic mutation carriers.

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.

Adult With PHOX2B Mutation and Late-Onset Congenital Central Hypoventilation Syndrome

ABSTRACT

PHOX2B 20/27 polyalanine repeat mutation (PARM) in patients with congenital central hypoventilation syndrome (CCHS) is generally associated with full-time ventilator dependence, Hirschsprung disease, and increased risk for cardiac asystole. We follow a 14-year-old boy with CCHS PHOX2B 20/27 PARM who is full-time ventilator dependent via tracheostomy and has Hirschsprung disease. His mother, age 52 years, has a history of prolonged recovery from anesthesia and an elevated serum bicarbonate level of 45 mEq/L discovered on routine blood chemistry. PHOX2B gene mutation analysis was performed and showed an identical 20/27 PARM, diagnostic of CCHS. Late-onset CCHS has been reported in those with 20/24, 20/25 PHOX2B PARM, and in nonpolyalanine repeat mutations. This is the first report of a patient with PHOX2B 20/27 PARM with a mild phenotype diagnosed during adulthood. This unusual presentation supports the screening for PHOX2B mutations in parents of children with CCHS.

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.

Conscious sedation with dexmedetomidine for implantation of a phrenic nerve stimulator in a pediatric case of late-onset congenital central hypoventilation syndrome

Patients with congenital central hypoventilation syndrome (CCHS) develop alveolar hypoventilation resulting from a failure of central ventilatory control. Late-onset CCHS (LO-CCHS), which may be precipitated by severe respiratory infection or exposure to sedatives or general anesthesia, presents after the neonatal period. Since CCHS patients require lifelong mechanical-assisted ventilation, in western countries, diaphragm pacing is used to provide adequate alveolar ventilation and oxygenation during rest and daily activities. The main anesthesia-related concern regarding CCHS is postoperative respiratory failure or apnea, and anesthetic agents should be minimized to avoid further respiratory depression after surgery. A 5-year-old girl with LO-CCHS was referred to our hospital for implantation of a phrenic nerve stimulator for diaphragm pacing. Respiratory infection triggered the need for permanent nocturnal ventilator support at age 3 years and tracheotomy was performed at age 4 years. Repeated self-dislodgement of the ventilator tube led to hypoxic ischemic encephalopathy. The patient was thought to require mechanical ventilation under minimum sedation and pain management during the early postoperative period. The co-administration of dexmedetomidine and morphine provided effective conscious sedation with protection of the surgical site and without adverse events. She was discharged from the intensive care unit with a home ventilator at 3 days post-operation.

Congenital central hypoventilation syndrome associated with Hirschsprung's Disease: case report and literature review

Objective:

To report the case of a newborn with recurrent episodes of apnea, diagnosed with Congenital Central hypoventilation syndrome (CCHS) associated with Hirschsprung's disease (HD), configuring Haddad syndrome.

Case description:

Third child born at full-term to a non-consanguineous couple through normal delivery without complications, with appropriate weight and length for gestational age. Soon after birth he started to show bradypnea, bradycardia and cyanosis, being submitted to tracheal intubation and started empiric antibiotic therapy for suspected early neonatal sepsis. During hospitalization in the NICU, he showed difficulty to undergo extubation due to episodes of desaturation during sleep and wakefulness. He had recurrent episodes of hypoglycemia, hyperglycemia, metabolic acidosis, abdominal distension, leukocytosis, increase in C-reactive protein levels, with negative blood cultures and suspected inborn error of metabolism. At 2 months of age he was diagnosed with long-segment Hirschsprung's disease and was submitted to segment resection and colostomy through Hartmann's procedure. A genetic research was performed by polymerase chain reaction for CCHS screening, which showed the mutated allele of PHOX2B gene, confirming the diagnosis.

Comments:

This is a rare genetic, autosomal dominant disease, caused by mutation in PHOX2B gene, located in chromosome band 4p12, which results in autonomic nervous system dysfunction. CCHS can also occur with Hirschsprung's disease and tumors derived from the neural crest. There is a correlation between phenotype and genotype, as well as high intrafamilial phenotypic variability. In the neonatal period it can simulate cases of sepsis and inborn errors of metabolism.

Congenital central hypoventilation syndrome associated with Hirschsprung's Disease: case report and literature review

OBJECTIVE

To report the case of a newborn with recurrent episodes of apnea, diagnosed with Congenital Central hypoventilation syndrome (CCHS) associated with Hirschsprung's disease (HD), configuring Haddad syndrome.

CASE DESCRIPTION

Third child born at full-term to a non-consanguineous couple through normal delivery without complications, with appropriate weight and length for gestational age. Soon after birth he started to show bradypnea, bradycardia and cyanosis, being submitted to tracheal intubation and started empiric antibiotic therapy for suspected early neonatal sepsis. During hospitalization in the NICU, he showed difficulty to undergo extubation due to episodes of desaturation during sleep and wakefulness. He had recurrent episodes of hypoglycemia, hyperglycemia, metabolic acidosis, abdominal distension, leukocytosis, increase in C-reactive protein levels, with negative blood cultures and suspected inborn error of metabolism. At 2 months of age he was diagnosed with long-segment Hirschsprung's disease and was submitted to segment resection and colostomy through Hartmann's procedure. A genetic research was performed by polymerase chain reaction for CCHS screening, which showed the mutated allele of PHOX2B gene, confirming the diagnosis.

COMMENTS

This is a rare genetic, autosomal dominant disease, caused by mutation in PHOX2B gene, located in chromosome band 4p12, which results in autonomic nervous system dysfunction. CCHS can also occur with Hirschsprung's disease and tumors derived from the neural crest. There is a correlation between phenotype and genotype, as well as high intrafamilial phenotypic variability. In the neonatal period it can simulate cases of sepsis and inborn errors of metabolism.