1p36 deletion syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

1p36 deletion syndrome is a disorder that typically causes intellectual disabilities. Most affected individuals do not speak or speak only a few words. They may have temper tantrums, bite themselves, or exhibit other behavior problems. Most have structural abnormalities of the brain, and seizures occur in more than half of individuals with this disorder. Affected individuals usually have weak muscle tone (hypotonia) and difficulty swallowing (dysphagia).

People with 1p36 deletion syndrome have a small head that is also unusually short and wide in proportion to its size (microbrachycephaly). Affected individuals also have distinctive facial features, including deep-set eyes with straight eyebrows; a sunken appearance of the middle of the face (midface hypoplasia); a broad, flat nose; a long area between the nose and mouth (philtrum); a pointed chin; and ears that are low-set, rotated backwards, and abnormally shaped.

People with 1p36 deletion syndrome often have unusually short fingers and toes (brachydactyly), permanently bent fingers and toes (camptodactyly), and short feet. They may also have vision or hearing problems. Some affected individuals have abnormalities of the skeleton, heart, gastrointestinal system, kidneys, or genitalia.

Life expectancy varies in people with 1p36 deletion syndrome, but affected individuals can survive into early adulthood.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

1p36 deletion syndrome is caused by the deletion of a piece of genetic material from a specific region in the short (p) arm of chromosome 1. In about 50 percent of people with this condition, the deleted region includes the tip of the p arm of chromosome 1. Around 29 percent of affected individuals have deletions that include a section near the end of the chromosome. The remaining 21 percent have complex rearrangements of genetic material that involve this region.

The size of the deletion varies among affected individuals. .cf0{font-style:italic;font-family:Segoe UI;font-size:9pt;}The signs and symptoms of 1p36 deletion syndrome are likely caused by the loss of multiple genes that are involved in the development of systems such as the brain, heart, and skeleton.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Most cases of 1p36 deletion syndrome are not inherited. They are the result of a chromosomal deletion that occurs as a random event during the formation of reproductive cells (eggs or sperm) or in early fetal development. Affected people typically have no history of the disorder in their family.

About 20 percent of people with 1p36 deletion syndrome inherit the chromosome with a deleted segment from an unaffected parent. In these cases, the parent carries a chromosomal rearrangement called a balanced translocation. No genetic material is gained or lost in a balanced translocation, so these chromosomal changes usually do not cause any health problems. However, translocations can become unbalanced as they are passed to the next generation. Children who inherit an unbalanced translocation can have a chromosomal rearrangement with extra or missing genetic material. Individuals with 1p36 deletion syndrome who inherit an unbalanced translocation are missing genetic material from the p arm of chromosome 1, which results in the health problems that are characteristic of this disorder.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

1p36 deletion syndrome is estimated to affect 1 in 5,000 newborns each year in the United States.

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 speech or vocalization · Very frequent (99-80%)

An abnormality in the sound (volume) or cadence (rate) of speech.

Absent speech · Very frequent (99-80%)

Complete lack of development of speech and language abilities.

Agenesis of corpus callosum · Very frequent (99-80%)

Absence of the corpus callosum as a result of the failure of the corpus callosum to develop, which can be the result of a failure in any one of the multiple steps of callosal development including cellular proliferation and migration, axonal growth or glial patterning at the midline.

Brachydactyly · Very frequent (99-80%)

Digits that appear disproportionately short compared to the hand/foot. The word brachydactyly is used here to describe a series distinct patterns of shortened digits (brachydactyly types A-E). This is the sense used here.

Camptodactyly of finger · Very frequent (99-80%)

The distal interphalangeal joint and/or the proximal interphalangeal joint of the fingers cannot be extended to 180 degrees by either active or passive extension.

Cerebral cortical atrophy · Very frequent (99-80%)

Atrophy of the cortex of the cerebrum.

Deeply set eye · Very frequent (99-80%)

An eye that is more deeply recessed into the plane of the face than is typical.

Delayed speech and language development · Very frequent (99-80%)

A degree of language development that is significantly below the norm for a child of a specified age.

Other findings in the same source

From: Orphanet

Additional reported features include EEG abnormality (Very frequent (99-80%)); Failure to thrive (Very frequent (99-80%)); Gait disturbance (Very frequent (99-80%)); Global developmental delay (Very frequent (99-80%)); Horizontal eyebrow (Very frequent (99-80%)); Hypotonia (Very frequent (99-80%)); Intellectual disability (Very frequent (99-80%)); Long philtrum (Very frequent (99-80%)); Midface retrusion (Very frequent (99-80%)); Pointed chin (Very frequent (99-80%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing 1p36 deletion syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

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.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for 1p36 deletion syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

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.