Congenital central hypoventilation syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

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

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

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.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

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.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

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.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormality of the autonomic nervous system · Very frequent (99-80%)

An abnormality of the autonomic nervous system.

Respiratory insufficiency · Very frequent (99-80%)

Aganglionic megacolon · Occasional (29-5%)

An abnormality resulting from a lack of intestinal ganglion cells (i.e., an aganglionic section of bowel) that results in bowel obstruction with enlargement of the colon.

Cognitive impairment · Occasional (29-5%)

Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering.

Ganglioneuroma · Occasional (29-5%)

A benign neoplasm that usually arises from the sympathetic trunk in the mediastinum, representing a tumor of the sympathetic nerve fibers arising from neural crest cells.

Hypotonia · Occasional (29-5%)

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

Neoplasm of the central nervous system · Occasional (29-5%)

A neoplasm of the central nervous system.

Neuroblastoma · Occasional (29-5%)

Neuroblastoma is a solid tumor that originate in neural crest cells of the sympathetic nervous system. Most neuroblastomas originate in the abdomen, and most abdominal neuroblastomas originate in the adrenal gland. Neuroblastomas can also originate in the thorax, usually in the posterior mediastinum.

Other findings in the same source

From: Orphanet

Additional reported features include Seizure (Occasional (29-5%)); Ganglioneuroblastoma (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Congenital central hypoventilation syndrome is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.