Extreme intra-familial variability of congenital central hypoventilation syndrome: a case series

IntroductionCongenital central hypoventilation syndrome is an autosomal dominant disorder that classically presents as sudden death in infancy secondary to central hypoventilation. Most cases are caused by polyalanine repeat mutations in the paired-like homeobox 2B gene, PHOX2B. More severe disease is typically associated with nonpolyalanine repeat mutations. We report the case of a family with nonpolyalanine repeat mutations that uncharacteristically has many individuals who were mildly symptomatic and only diagnosed after genetic testing. We highlight the highly variable clinical presentation of this condition and the need for clinicians to remain vigilant.Case presentationWe identified 10 individuals in a large extended Caucasian family of German and Austrian background with congenital central hypoventilation syndrome. A 16-year old male proband presented for reproductive counseling. He had a previous history of apneic spells and Hirschsprung disease in the neonatal period. A PHOX2B nonpolyalanine repeat mutation was identified in the proband and used to screen his extended family.Cases 2 to 10: Several mildly symptomatic family members (males aged 5, 13, 42 and 80 years; females aged 28, 44, 46 and 48 years) spanning four generations were identified after genetic screening. A newborn boy from this family was also recently diagnosed with Hirschsprung disease and went on to have an abnormal sleep study.ConclusionsIn this report, we highlight the significant phenotypic variability of congenital central hypoventilation syndrome, previously thought to be a rare genetic condition. Given the extreme clinical variability, it is possible that the prevalence of congenital central hypoventilation syndrome in the general population is much higher than previous estimates. This is of major importance to all clinicians who will need to maintain a high index of suspicion for this not so rare and highly clinically variable genetic condition that spans all ages. As the familial mutation has been identified, presymptomatic and prenatal diagnostic testing are available options for family members.

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title: An official ATS clinical policy statement: Congenital central hypoventilation syndrome: genetic basis, diagnosis, and management.
abstract: Congenital central hypoventilation syndrome (CCHS) is characterized by alveolar hypoventilation and autonomic dysregulation.



(1) To demonstrate the importance of PHOX2B testing in diagnosing and treating patients with CCHS, (2) to summarize recent advances in understanding how mutations in the PHOX2B gene lead to the CCHS phenotype, and (3) to provide an update on recommendations for diagnosis and treatment of patients with CCHS.



Committee members were invited on the basis of their expertise in CCHS and asked to review the current state of the science by independently completing literature searches. Consensus on recommendations was reached by agreement among members of the Committee.



A review of pertinent literature allowed for the development of a document that summarizes recent advances in understanding CCHS and expert interpretation of the evidence for management of affected patients.



A PHOX2B mutation is required to confirm the diagnosis of CCHS. Knowledge of the specific PHOX2B mutation aids in anticipating the CCHS phenotype severity. Parents of patients with CCHS should be tested for PHOX2B mutations. Maintaining a high index of suspicion in cases of unexplained alveolar hypoventilation will likely identify a higher incidence of milder cases of CCHS. Recommended management options aimed toward maximizing safety and optimizing neurocognitive outcome include: (1) biannual then annual in-hospital comprehensive evaluation with (i) physiologic studies during awake and asleep states to assess ventilatory needs during varying levels of activity and concentration, in all stages of sleep, with spontaneous breathing, and with artificial ventilation, and to assess ventilatory responsiveness to physiologic challenges while awake and asleep, (ii) 72-hour Holter monitoring, (iii) echocardiogram, (iv) evaluation of ANS dysregulation across all organ systems affected by the ANS, and (v) formal neurocognitive assessment; (2) barium enema or manometry and/or full thickness rectal biopsy for patients with a history of constipation; and (3) imaging for neural crest tumors in individuals at greatest risk based on PHOX2B mutation.

title: Congenital central hypoventilation syndrome: not just another rare disorder.
abstract: Congenital central hypoventilation syndrome (CCHS) is a rare syndrome, present from birth, and is defined as the failure of automatic control of breathing. Patients have absent or negligible ventilatory sensitivity to hypercapnia and hypoxaemia during sleep and wakefulness. Therefore, especially while asleep, children with CCHS experience progressive hypercapnia and hypoxaemia. They lack arousal responses and sensations of dyspnoea to the endogenous challenges of isolated hypercapnia and hypoxaemia and to the combined stimulus of hypercapnia and hypoxaemia. Patients with CCHS do not exhibit signs of respiratory distress when challenged with hypercarbia or hypoxia. The diagnosis is one of exclusion, ruling out any primary pulmonary, cardiac, metabolic or neurologic cause for central hypoventilation. CCHS is associated with other manifestations of autonomic nervous system dysfunction, including Hirschsprung's disease. All patients with CCHS require lifelong ventilatory support during sleep but some will be able to maintain adequate ventilation without assistance while awake once past infancy. However, some CCHS patients require ventilatory support for 24h/day. Modalities of home mechanical-assisted ventilation include positive pressure ventilation via tracheostomy, non-invasive positive pressure ventilation (bi-level ventilation), negative pressure ventilation and diaphragmatic pacers. Supplemental oxygen alone is inadequate treatment. With early diagnosis and adequate ventilatory support, these children can have good outcomes and lead productive lives.

title: Late-onset central hypoventilation syndrome: a family genetic study
abstract: Congenital central hypoventilation syndrome is a rare disorder characterised by chronic alveolar hypoventilation, which becomes more pronounced during sleep and may be associated with neurocristopathies, such as Hirchsprung's disease. A mutation in the PHOX2B gene has recently been identified. In a family of both parents and five offspring, detailed clinical assessment, pulmonary function testing, overnight sleep studies and ventilatory responsiveness to progressive hypercapnia (V′R,CO2) were performed, in addition to analysis of known genetic loci for this condition. The father and four of the offspring demonstrated features of central hypoventilation with nonapnoeic oxygen desaturation during sleep and diminished V′R,CO2, despite normal pulmonary function. The lowest sleep saturation was median (range) 79% (67–83%) and V′R,CO2 was 2.1 (0.03–4.3) L·min-1·kPa-1. The normal values for the authors’ centre (St Vincent's University Hospital, Dublin, Ireland) are 15–40 L·min-1·kPa-1. An in-frame five amino acid polyalanine expansion of the PHOX2B gene was found in all affected subjects, while the mother and fifth child, who did not have features of central hypoventilation, had a normal PHOX2B gene. Magnetic resonance imaging of the brainstem in one severely affected child was normal. The present study of a unique family confirms that transmission of late-onset congenital central hypoventilation syndrome is autosomal dominant in nature.

title: PHOX2B mutation-confirmed congenital central hypoventilation syndrome in a Chinese family: presentation from newborn to adulthood.
abstract: Congenital central hypoventilation syndrome (CCHS) is characterized by compromised chemoreflexes resulting in sleep hypoventilation. We report a Chinese family with paired-like homeobox 2B (PHOX2B) mutation-confirmed CCHS, with a clinical spectrum from newborn to adulthood, to increase awareness of its various manifestations.



After identifying central hypoventilation in an adult man (index case), clinical evaluation was performed on the complete family, which consisted of the parents, five siblings, and five offspring. Pulmonary function tests, overnight polysomnography, arterial blood gas measurements, hypercapnia ventilatory response, and PHOX2B gene mutation screening were performed on living family members. Brain MRI, 24-h Holter monitoring, and echocardiography were performed on members with clinically diagnosed central hypoventilation.



The index patient and four offspring manifested clinical features of central hypoventilation. The index patients had hypoxia and hypercapnia while awake, polycythemia, and hematocrit levels of 70%. The first and fourth children had frequent cyanotic spells, and both died of respiratory failure. The second and third children remained asymptomatic until adulthood, when they experienced impaired hypercapnic ventilatory response. The third child had nocturnal hypoventilation with nadir pulse oximetric saturation of 59%. Adult-onset CCHS with PHOX2B gene mutation of the + 5 alanine expansions were confirmed in the index patient and the second and third children. The index patient and the third child received ventilator support system bilevel positive airway pressure treatment, which improved the hypoxemia, hypercapnia, and polycythemia without altering their chemosensitivity.



Transmission of late-onset CCHS is autosomal-dominant. Genetic screening of family members of CCHS probands allows for early diagnosis and treatment.

title: Congenital central hypoventilation syndrome with PHOX2B gene mutation in a Taiwanese infant.
abstract: Congenital central hypoventilation syndrome (CCHS) is a rare disease that is characterized by failure in the autonomic control of breathing. Recent reports have identified mutation of the paired mesoderm homeobox protein 2b (PHOX2B) gene as playing a major role in CCHS. Increasing polyalanine repeat number is associated with a more severe clinical phenotype. We report a newborn male infant with the clinical manifestations of apnea and cyanosis requiring immediate endotracheal intubation at the age of 1 day. Recurrent hypoventilation with hypercapnia and hypoxemia occurred during sleep after weaning from the ventilator. No primary cardiopulmonary disease was identified. These clinical manifestations are compatible with CCHS. PHOX2B gene mutation analysis performed at the age of 4 months revealed expanded alleles containing polyalanine 26 repeats, further supporting the diagnosis of CCHS. Continuous ventilator support was necessary and tracheostomy was ultimately performed at the age of 5 months due to ventilator dependence. He was discharged with home ventilator support at the age of 6 months.

title: The French Congenital Central Hypoventilation Syndrome Registry: general data, phenotype, and genotype.
abstract: To analyze the main clinical features, genetic mutations, and outcomes of patients of the French Congenital Central Hypoventilation Syndrome (CCHS) Registry.



A country-wide cohort established throughout a long-term multicenter effort.



Seventy French patients with CCHS (29 male patients and 41 female patients).



The following items were analyzed: the most important moments of the disease course; the main clinical characteristics; associated pathologic conditions; management; clinical outcome; and genetic mutations.



An average of four new cases of CCHS per year was observed in the last 5 years. Thus, the incidence may be estimated to be 1 per 200,000 live births in France. The median age at diagnosis was 3.5 months (range, 0.5 to 15 months) before 1995 and < 2 weeks in the last 5 years (p = 0.01). CCHS occurred in isolation in 58 of 70 patients. In the remainder, it was associated with Hirschsprung disease (HSCR) [nine patients], Hirschsprung and neural crest tumor (two patients), and growth hormone deficiency (one patient). Among the 50 patients who lived beyond 1 year of age, all but one received nighttime ventilation, with 10 of them (20%) receiving it noninvasively. Three patients (6%) required daytime ventilatory support in addition to nighttime ventilation. The overall mortality rate was 38% (95% confidence interval [CI], 27 to 49%). The median age at death was 3 months (range, 0.4 months to 21 years). The 2-year mortality rate was greater in male patients than in female patients (p = 0.02; relative risk [RR], 2.71; 95% CI, 1.14 to 6.47) but was not affected by HSCR (p = 0.93; RR, 0.95; 95% CI, 0.28 to 3.2). The 43 patients who are currently alive (11 men; sex ratio, 0.4) have a mean age of 9 years (range, 2 months to 27 years). Among the 34 patients tested thus far, heterozygous mutations of the paired-like homeobox gene 2B (PHOX2B) gene were found in 31 patients (91%).



Our four major findings are the extreme rarity of CCHS, the improved recognition over time, the lack of effect of HSCR on the mortality rate, and the high frequency of PHOX2B mutations.

title: Effect of sleep stage on breathing in children with central hypoventilation.
abstract: The early literature suggests that hypoventilation in infants with congenital central hypoventilation syndrome (CHS) is less severe during rapid eye movement (REM) than during non-REM (NREM) sleep. However, this supposition has not been rigorously tested, and subjects older than infancy have not been studied. Given the differences in anatomy, physiology, and REM sleep distribution between infants and older children, and the reduced number of limb movements during REM sleep, we hypothesized that older subjects with CHS would have more severe hypoventilation during REM than NREM sleep. Nine subjects with CHS, aged (mean +/- SD) 13 +/- 7 yr, were studied. Spontaneous ventilation was evaluated by briefly disconnecting the ventilator under controlled circumstances. Arousal was common, occurring in 46% of REM vs. 38% of NREM trials [not significant (NS)]. Central apnea occurred during 31% of REM and 54% of NREM trials (NS). Although minute ventilation declined precipitously during both REM and NREM trials, hypoventilation was less severe during REM (drop in minute ventilation of 65 +/- 23%) than NREM (drop of 87 +/- 16%, P = 0.036). Despite large changes in gas exchange during trials, there was no significant change in heart rate during either REM or NREM sleep. We conclude that older patients with CHS frequently have arousal and central apnea, in addition to hypoventilation, when breathing spontaneously during sleep. The hypoventilation in CHS is more severe during NREM than REM sleep. We speculate that this may be due to increased excitatory inputs to the respiratory system during REM sleep.

title: Congenital central hypoventilation syndrome and Hirschsprung’s disease
abstract: Five cases of the Hirschsprung’s disease–congenital central hypoventilation syndrome (CCHS) association are presented and 41 other published cases reviewed. These children have a distinct pattern of associated features, an equal sex incidence, and a characteristic spectrum of disease severity which suggests that the condition is genetically distinct from other cases of Hirschsprung’s disease. While approximately 1.5% of Hirschsprung’s disease patients, and 10% of those with total colonic aganglionosis, will have CCHS, up to 50% of CCHS patients will have Hirschsprung’s disease. Approximately 20% of CCHS/Hirschsprung patients will also have neuroblastoma or ganglioneuroma, usually multiple. Abnormalities of the eye and autonomic nervous system are also common. The ventilatory abnormality is usually evident on the first day of life. The aganglionosis is also severe, with more than half (59%) of the patients having aganglionosis extending into the small bowel.

title: Congenital central hypoventilation syndrome: genotype–phenotype correlation in parents of affected children carrying a PHOX2B expansion mutation
abstract: Parodi S, Vollono C, Baglietto MP, Balestri M, Di Duca M, Landri PA, Ceccherini I, Ottonello G, Cilio MR. Congenital central hypoventilation syndrome: genotype–phenotype correlation in parents of affected children carrying a PHOX2B expansion mutation.

title: Presentation and treatment of monozygotic twins with congenital central hypoventilation syndrome.
abstract: Congenital central hypoventilation syndrome is a rare genetic disorder characterized by hypoventilation during sleep secondary to a blunted response to hypercapnia and hypoxia. The current case report describes developmentally normal four-year-old monozygotic twin boys who presented in infancy with variable presentations and clinical severity of congenital central hypoventilation syndrome. Both were managed with noninvasive positive pressure ventilation.

title: Congenital central hypoventilation syndrome from past to future: Model for translational and transitional autonomic medicine
abstract: The modern story of CCHS began in 1970 with the first description by Mellins et al., came most visibly to the public eye with the ATS Statement in 1999, and continues with increasingly fast paced advances in genetics. Affected individuals have diffuse autonomic nervous system dysregulation (ANSD). The paired‐like homeobox gene PHOX2B is the disease‐defining gene for CCHS; a mutation in the PHOX2B gene is requisite to the diagnosis of CCHS. Approximately 90% of individuals with the CCHS phenotype will be heterozygous for a polyalanine repeat expansion mutation (PARM); the normal allele will have 20 alanines and the affected allele will have 24–33 alanines (genotypes 20/24–20/33). The remaining ∼10% of individuals with CCHS will have a non‐PARM (NPARM), in the PHOX2B gene; these will be missense, nonsense, or frameshift. CCHS and PHOX2B are inherited in an autosomal dominant manner with a stable mutation. Approximately 8% of parents of a CCHS proband will be mosaic for the PHOX2B mutation. A growing number of cases of CCHS are identified after the newborn period, with presentation from infancy into adulthood. An improved understanding of the molecular basis of the PHOX2B mutations and of the PHOX2B genotype/CCHS phenotype relationship will allow physicians to anticipate the clinical phenotype for each affected individual. To best convey the remarkable history of CCHS, and to describe the value of recognizing CCHS as a model for translational and transitional autonomic medicine, we present this review article in the format of a chronological story, from 1970 to the present day. Pediatr Pulmonol. 2009;