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

Airway obstruction in two children with congenital central hypoventilation syndrome and review of the literature

Congenital central hypoventilation syndrome (CCHS) is an autosomal dominant disease that is caused by heterozygous mutations in the paired-like homeobox 2B gene (PHOX2B). Madani et al. described an abnormally high degree of not only central apnea but also obstructive and mixed apnea in Phox2b27Ala/+newborn mice. Newborns with CCHS must undergo polysomnography for obstructive respiratory events in order to guide the optimal ventilation strategy if oxygen desaturation, bradycardia, and malaise persist under noninvasive ventilation. Newborns and infants with CCHS must be systematically tested for obstructive apnea, especially in cases of inefficient noninvasive ventilation.

Images: Atypical presentation of congenital central hypoventilation syndrome in an infant with central and obstructive sleep apnea

Congenital central hypoventilation syndrome (CCHS), a rare disease caused by paired-like homeobox 2B variants, affects control of breathing. We report on a 21-month-old boy with CCHS caused by a novel nonpolyalanine repeat mutation, neuroblastoma, severe obstructive and central sleep apnea, and sleep-related hypoxemia without hypoventilation. At 10 months, due to persistent central sleep apnea during serial polysomnography, bilevel positive airway pressure therapy was initiated despite the absence of hypoventilation. Nonpolyalanine repeat mutations are associated with severe phenotypes requiring continuous assisted ventilation, Hirschsprung's disease, and neural crest tumors; however, our patient had a relatively milder respiratory phenotype requiring sleep-only assisted ventilation without tracheostomy. Although alveolar hypoventilation is the hallmark of CCHS, our patient lacked hypoventilation. Bilevel positive airway pressure could be considered in some infants with CCHS requiring sleep-only assisted ventilation for tracheostomy avoidance. Our case demonstrates the expanding phenotypic spectrum in CCHS and the importance of formulating an individualized care plan.

CITATION

Fain ME, Raghunandan S, Pencheva B, Leu RM, Kasi AS. Images: atypical presentation of congenital central hypoventilation syndrome in an infant with central and obstructive sleep apnea. J Clin Sleep Med. 2024;20(3):478-481.

Obstructive sleep apnea as a presentation of congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome is a rare disorder due to a mutation in the PHOX2B gene, characterized by a failure in autonomic control of breathing with diminished or absent response to hypoxia and hypercapnia, which is most pronounced during sleep. Most patients present from birth with central apneas and hypoventilation, or later in the setting of a physiologic stress. Recent literature in mice with a Phox2b27Ala/+ mutation suggests a predisposition to obstructive apneas likely due to hypoglossal dysgenesis. We report on three patients with obstructive sleep apneas with absent or mild hypoventilation. Our cases propose that obstructive apneas can be the primary presentation in patients who subsequently develop the classic phenotype of congenital central hypoventilation syndrome and emphasize their close monitoring and surveillance.

CITATION

Kagan O, Zhang C, McElyea C, Keens TG, Davidson Ward SL, Perez IA. Obstructive sleep apnea as a presentation of congenital central hypoventilation syndrome. J Clin Sleep Med. 2023;19(9):1697-1700.

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.

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.

Congenital Central Hypoventilation Syndrome: Diagnosis and Long-Term Ventilatory Outcomes

Background

Congenital central hypoventilation syndrome (CCHS), a rare disease caused by variants in the paired-like homeobox 2B (PHOX2B) gene, affects regulation of respiration necessitating lifelong assisted ventilation (AV). Most patients require full-time AV during infancy and some patients may sustain adequate spontaneous ventilation during wakefulness and change AV modalities at a later age. The aims of this study were to assess the changes in duration and modalities of AV, long-term respiratory outcomes, and to correlate them with PHOX2B genotypes.

Methods

We conducted a retrospective study of patients with CCHS treated at our institution between January 1997 and May 2022. Results analyzed included: clinical presentation, PHOX2B genotype, modality and duration of AV at diagnosis and follow-up, survival, and transition to adult care.

Results

We identified 30 patients with CCHS-8 with PHOX2B nonpolyalanine repeat mutations (NPARMs), 21 with polyalanine repeat mutations (PARMs), and 1 with unknown PHOX2B genotype. The median age at presentation was 0.25 months (IQR 0.1-0.7 months). At diagnosis of CCHS, 24 (80%) patients required continuous AV and 28 (93%) received AV via tracheostomy. Twenty-six patients required sleep-only AV at a median age of 9 months (IQR 6-14 months). Nine patients requiring sleep-only AV underwent tracheostomy decannulation at a median age of 11.2 years (IQR 5.9-15.7 years) and used noninvasive positive pressure ventilation or diaphragm pacing. There was insufficient evidence to conclude that patients with PARMs and NPARMs differed by age at presentation (P = .39), tracheostomy (P = .06), and transition to sleep-only AV (P = .9). Six patients transitioned to adult care, 23 continued receiving pediatric care, and 1 patient died due to complications from Hirschsprung's disease.

Conclusion

Our study demonstrates prolonged survival and good long-term respiratory outcomes possibly related to the early diagnosis of CCHS, optimizing AV strategies, and multidisciplinary care. The increasing number of patients attaining adulthood highlights the necessity for multidisciplinary care for adults with CCHS.

Impaired ventilation during 6-min walk test in congenital central hypoventilation syndrome

BACKGROUND

Patients with congenital central hypoventilation syndrome (CCHS) can develop hypoxemia and hypercapnia during exercise. However, there is limited literature on cardiorespiratory responses during submaximal exercise and their correlation with paired-like homeobox 2B (PHOX2B) genotype.

OBJECTIVES

To assess oxygen saturation (SpO₂ ), end-tidal carbon dioxide (ETCO₂ ), heart rate (HR), and 6-min walk distance (6MWD) during a 6-min walk test (6MWT) in CCHS subjects and to correlate them with PHOX2B genotypes and assisted ventilation (AV) via tracheostomy.

METHODS

In this cross-sectional study, subjects with CCHS performed 6MWT with continuous pulse oximetry, HR, and capnography recorded before and during the 6MWT. Medical records were reviewed for PHOX2B genotype and phenotype data. Patients were categorized based on PHOX2B genotype and AV via tracheostomy.

RESULTS

Fifteen subjects aged 10.5 (interquartile range 7.9-16.2) years completed the 6MWT. Nine subjects used AV via tracheostomy. Seven (47%) subjects developed hypoxemia (SpO₂  ≤ 90%, n = 7) and hypoventilation (ETCO₂  ≥ 50 mmHg, n = 3) during the 6MWT. There was a significant decline from baseline SpO₂ , increase from baseline ETCO₂ , and increase in HR during the 6MWT (all p < 0.05). Subjects had decreased median percent predicted 6MWD (59.7% [50.6%-62.5%]). Nadir SpO₂ (p = 0.029) and peak ETCO₂ (p = 0.046) differed significantly between PHOX2B genotype groups but 6MWD did not (p = 0.8).

CONCLUSION

Despite normal oxygenation and ventilation at rest and during sleep on AV, patients with CCHS can develop hypoxemia and hypercapnia during submaximal exercise. Our study highlights the importance of assessing ventilatory responses during submaximal exercise in patients with CCHS regardless of their PHOX2B genotype.

Congenital central hypoventilation syndrome: a life-threatening cause of neonatal apnoea

Congenital central hypoventilation syndrome (CCHS) is an uncommon genetic disease characterised by an autonomic nervous system dysfunction that affects ventilatory homeostasis. Involvement of other systems is also described, mainly cardiovascular, gastrointestinal and central nervous systems. We describe a rare case of CCHS diagnosed in a term newborn who presented with persistent apnoea in the first hours of life. After an exhaustive aetiological study excluding primary pulmonary, cardiac, metabolic and neurological diseases, this diagnosis was confirmed by a paired-like homeobox 2B gene sequence analysis. During hospitalisation, ventilation was optimised and multidisciplinary follow-up was initiated, including genetic counselling. At 2 months old, the child was discharged under non-invasive ventilation during sleep. This case illustrates the importance of early diagnosis, including genetic study and advances in home ventilation. These factors allow early hospital discharge and timely multidisciplinary intervention, which is crucial for patients' quality of life and outcome optimisation.