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    Congenital Central Hypoventilation Syndrome

    Subjects: Genetics
    View times: 5
    Submitted by: Nicole Yin
    (This entry belongs to Entry Collection "MedlinePlus ")

    Definition

    Congenital central hypoventilation syndrome (CCHS) is a disorder that affects normal breathing.

    1. Introduction

    People with this disorder take shallow breaths (hypoventilate), especially during sleep, resulting in a shortage of oxygen and a buildup of carbon dioxide in the blood. Ordinarily, the part of the nervous system that controls involuntary body processes (autonomic nervous system) would react to such an imbalance by stimulating the individual to breathe more deeply or wake up. This nervous system reaction is impaired in people with CCHS. They must be supported with a machine to help them breathe (mechanical ventilation) or a device that stimulates a normal breathing pattern (diaphragm pacemaker). Some affected individuals need this support 24 hours a day, while others need it only at night.

    Symptoms of CCHS usually become apparent shortly after birth when affected infants hypoventilate upon falling asleep. In these infants, a lack of oxygen in the blood often causes a bluish appearance of the skin or lips (cyanosis). In some milder cases, CCHS may not become apparent until later in life.

    In addition to the breathing problem, people with CCHS may have difficulty regulating their heart rate and blood pressure, for example, in response to exercise or changes in body position. They also have decreased perception of pain, low body temperature, and occasional episodes of heavy sweating.

    People with CCHS may have additional problems affecting the nervous system. About 20 percent of people with CCHS have abnormalities in the nerves that control the digestive tract (Hirschsprung disease), resulting in severe constipation, intestinal blockage, and enlargement of the colon. (Some researchers refer to the combination of CCHS and Hirschsprung disease as Haddad syndrome.) Some affected individuals develop learning difficulties or other neurological problems. People with CCHS are also at increased risk of developing certain tumors of the nervous system called neuroblastomas, ganglioneuromas, and ganglioneuroblastomas.

    Additionally, individuals with CCHS usually have eye abnormalities, including a decreased response of the pupils to light. People with CCHS, especially children, may have a characteristic appearance with a short, wide, somewhat flattened face often described as "box-shaped."

    In CCHS, life expectancy and the extent of any intellectual disabilities depend on the severity of the disorder, timing of the diagnosis, and the success of treatment.

    2. Frequency

    CCHS is a relatively rare disorder. More than 1,000 individuals with this condition have been identified. Researchers believe that some cases of sudden infant death syndrome (SIDS) or sudden unexplained death in children may be caused by undiagnosed CCHS.

    3. Causes

    Mutations in a gene called PHOX2B cause CCHS. The PHOX2B gene provides instructions for making a protein that is important during development before birth. The PHOX2B protein helps support the formation of nerve cells (neurons) and regulates the process by which the neurons mature to carry out specific functions (differentiation). The protein is active in the neural crest, which is a group of cells in the early embryo that give rise to many tissues and organs. Neural crest cells migrate to form parts of the autonomic nervous system, many tissues in the face and skull, and other tissue and cell types.

    PHOX2B gene mutations that cause CCHS are believed to interfere with the PHOX2B protein's role in supporting neuron formation and differentiation, especially in the autonomic nervous system. As a result, bodily functions that are controlled by this system, including regulation of breathing, heart rate, blood pressure, and body temperature, are inconsistent in CCHS.

    4. Inheritance

    This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

    More than 90 percent of cases of CCHS result from new mutations in the PHOX2B gene. These cases occur in people with no history of the disorder in their family. Occasionally an affected person inherits the mutation from one affected parent. The number of such cases has been increasing as better treatment has allowed more affected individuals to live into adulthood and start families.

    About 5 to 10 percent of affected individuals inherit the altered gene from an unaffected parent who has a PHOX2B gene mutation only in their sperm or egg cells. This phenomenon is called germline mosaicism. A parent with mosaicism for a PHOX2B gene mutation may not show any signs or symptoms of CCHS.

    5. Other Names for This Condition

    • CCHS
    • congenital central hypoventilation
    • congenital failure of autonomic control
    • Haddad syndrome
    • Ondine syndrome
    • Ondine-Hirschsprung disease

    The entry is from https://medlineplus.gov/genetics/condition/congenital-central-hypoventilation-syndrome

    References

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    2. Berry-Kravis EM, Zhou L, Rand CM, Weese-Mayer DE. Congenital centralhypoventilation syndrome: PHOX2B mutations and phenotype. Am J Respir Crit CareMed. 2006 Nov 15;174(10):1139-44.
    3. Di Lascio S, Benfante R, Di Zanni E, Cardani S, Adamo A, Fornasari D,Ceccherini I, Bachetti T. Structural and functional differences in PHOX2Bframeshift mutations underlie isolated or syndromic congenital centralhypoventilation syndrome. Hum Mutat. 2018 Feb;39(2):219-236. doi:10.1002/humu.23365.
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    6. Paglietti MG, Cherchi C, Porcaro F, Agolini E, Schiavino A, Petreschi F,Novelli A, Cutrera R. Two novel mutations in exon 3 of PHOX2B gene: think aboutcongenital central hypoventilation syndrome in patients with Hirschsprungdisease. Ital J Pediatr. 2019 Apr 18;45(1):49. doi: 10.1186/s13052-019-0636-8.
    7. Parodi S, Bachetti T, Lantieri F, Di Duca M, Santamaria G, Ottonello G, MateraI, Ravazzolo R, Ceccherini I. Parental origin and somatic mosaicism of PHOX2Bmutations in Congenital Central Hypoventilation Syndrome. Hum Mutat. 2008Jan;29(1):206.
    8. Repetto GM, Corrales RJ, Abara SG, Zhou L, Berry-Kravis EM, Rand CM,Weese-Mayer DE. Later-onset congenital central hypoventilation syndrome due to a heterozygous 24-polyalanine repeat expansion mutation in the PHOX2B gene. ActaPaediatr. 2009 Jan;98(1):192-5. doi: 10.1111/j.1651-2227.2008.01039.x.
    9. Sasaki A, Kishikawa Y, Imaji R, Fukushima Y, Nakamura Y, Nishimura Y, YamadaM, Mino Y, Mitsui T, Hayasaka K. Novel PHOX2B mutations in congenital centralhypoventilation syndrome. Pediatr Int. 2019 Apr;61(4):393-396. doi:10.1111/ped.13812.
    10. Todd ES, Weinberg SM, Berry-Kravis EM, Silvestri JM, Kenny AS, Rand CM, ZhouL, Maher BS, Marazita ML, Weese-Mayer DE. Facial phenotype in children and young adults with PHOX2B-determined congenital central hypoventilation syndrome:quantitative pattern of dysmorphology. Pediatr Res. 2006 Jan;59(1):39-45.
    11. Weese-Mayer DE, Berry-Kravis EM, Ceccherini I, Keens TG, Loghmanee DA, TrangH; ATS Congenital Central Hypoventilation Syndrome Subcommittee. An official ATS clinical policy statement: Congenital central hypoventilation syndrome: geneticbasis, diagnosis, and management. Am J Respir Crit Care Med. 2010 Mar15;181(6):626-44. doi: 10.1164/rccm.200807-1069ST.
    12. Weese-Mayer DE, Marazita ML, Rand CM, Berry-Kravis EM. Congenital CentralHypoventilation Syndrome. 2004 Jan 28 [updated 2014 Jan 30]. In: Adam MP,Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors.GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle;1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1427/
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