BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is a rare autosomal dominant disease that is mainly caused by PHOX2B mutations. The purpose of this study is to analyze and summarize the clinical and genetic characteristics of CCHS patients in the Chinese population from our study and previous literature.
METHODS: The potential pathogenic gene mutations of CCHS were identified and verified by next generation sequencing combined with Sanger sequencing, fluorescent probe PCR and capillary electrophoresis. The clinical characteristics and gene mutations of CCHS cases in Chinese population were summarized from our study and previous literature to explore the genotype-phenotype correlations.
RESULTS: We identified 48 CCHS cases including three new cases from our report in China. Overall, 77.1% of the patients had PHOX2B polyalanine repeat expansion mutations (PARMs), and the remaining 22.9% had 10 distinct PHOX2B non-polyalanine repeat expansion mutations (NPARMs). Compared to those with PARMs, patients with NPARMs were more likely to have premature birth (54.5% vs. 2.8%, p < 0.001) and lower birth weight (33.3% vs. 3.2%, p = 0.030), with statistical significance. The patients with PARMs were more likely to have cardiovascular defects (64.9% vs. 27.3%, p = 0.063), cerebral hemorrhage (29.7% vs. 9.1%, p = 0.322) and seizures (37.8% vs. 9.1%, p = 0.151) than those with NPARMs, with no statistical significance.
CONCLUSIONS: CCHS patients with PHOX2B NPARMs were more likely to have premature birth and low birth weight, while PHOX2B PARMs tended to be positively associated with the risk of cardiovascular defects, cerebral hemorrhage and seizures in Chinese population.

We present a rare case of a 2-year-old male patient referred for primary evaluation of constipation and ultimately treatment of Hirschsprung disease (HSCR) whose preoperative workup incidentally revealed a posterior paraspinal mass. Following the biopsy of the mass, the patient exhibited hypoventilation and hypoxia requiring a delayed extubation, raising suspicion for congenital central hypoventilation syndrome (CCHS). We focus on the known history of associations between HSCR and CCHS, in addition to recently found genetic mutations in paired-like homeobox 2B that link HSCR, CCHS, and neuroblastoma.

BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is a rare disorder characterized by alveolar hypoventilation and autonomic system dysregulation secondary to mutations of the PHOX2B gene. Treatment consists of assisted ventilation using positive-pressure ventilators via tracheostomy, bi-level positive airway pressure (BPAP) via a noninvasive interface, negative-pressure ventilators, or diaphragm pacing. The long-term use of BPAP in younger children at home has been less frequently reported.
METHODS: We present a case of a 2-month-old infant with CCHS who was successfully managed by BPAP without the need for tracheostomy and followed up for 7 years.
CONCLUSIONS: CCHS is a rare disease that manifests as nocturnal desaturation and carbon dioxide retention in early life. Noninvasive ventilation can be successfully used in young infants via an appropriate mask.

Paired-like homeobox (PHOX)2B is considered to be the causative gene of congenital central hypoventilation syndrome (CCHS), a dominant genetic disorder that results in abnormal central respiratory control with resulting hypoventilation during sleep. In this study, we report a novel c.676_677insG (p.Ala226fs) mutation in a patient with severe CCHS, and we evaluated the function of this mutation. The mutation reduced the translation of the mutant PHOX2B protein and impaired its ability to activate the PHOX2A promoter, due to a haploinsufficiency effect. The mutant PHOX2B was able to interact with wildtype PHOX2B, resulting in retention of PHOX2B on the nuclear membrane, which may impair the normal function of the nuclear membrane, and leading to cellular morbidity. Our study provides useful information for the functional studies of PHOX2B and understanding the pathogenesis of CCHS, and thus is beneficial for the prognosis of, genetic counseling for, and development of pharmaceuticals for PHOX2B-associated diseases.

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.