Chromosome 1p36 deletion syndrome

Alternate names

1p36 deletion syndrome; Monosomy 1p36 syndrome

Definition

1p36 deletion syndrome is a chromosome disorder that typically causes severe intellectual disability.

Epidemiology

1p36 deletion syndrome is believed to affect between 1 in 5,000 and 1 in 10,000 newborns. However, this may be an underestimate because some affected individuals are likely never diagnosed.

Cause

• 1p36 deletion syndrome is caused by a deletion of genetic material from a specific region in the short (p) arm of chromosome 1.
• The signs and symptoms of 1p36 deletion syndrome are probably related to the loss of multiple genes in this region.
• The size of the deletion varies among affected individuals.

Inheritance

• Most cases of 1p36 deletion syndrome are not inherited.
• They result from 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, in which no genetic material is gained or lost. Balanced translocations usually do not cause any health problems; however, they 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 short arm of chromosome 1, which results in birth defects and other health problems characteristic of this disorder.

Signs and symptoms

• 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 swallowing difficulties (dysphagia).
• Other features include a small head that is unusually short and wide; vision and hearing problems; abnormalities of the skeleton, heart, gastrointestinal system, kidneys, or genitalia; and distinctive facial features.

Clinical presentation

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.

80%-99% of people have these symptoms

• Absent speech(Absent speech development)
• Agenesis of corpus callosum
• Brachydactyly(Short fingers or toes)
• Camptodactyly of finger(Permanent flexion of the finger)
• Cerebral cortical atrophy(Decrease in size of the outer layer of the brain due to loss of brain cells)
• Deeply set eye(Deep set eye)
• EEG abnormality
• Failure to thrive(Faltering weight)
• Gait disturbance(Abnormal gait)
• Global developmental delay
• Horizontal eyebrow(Flat eyebrow)
• Intellectual disability(Mental deficiency)
• Long philtrum
• Midface retrusion(Decreased size of midface)
• Muscular hypotonia(Low or weak muscle tone)
• Pointed chin(Pointy chin)
• Poor speech
• Short foot(Short feet)
• Ventriculomegaly
• Wide nasal bridge(Broad nasal bridge)

30%-79% of people have these symptoms

• Autism
• Brachycephaly(Short and broad skull)
• Clinodactyly of the 5th finger(Permanent curving of the pinkie finger)
• Constipation
• Delayed cranial suture closure
• Depressed nasal bridge(Depressed bridge of nose)
• Depressed nasal ridge(Flat nose)
• Dysphagia(Poor swallowing)
• Epicanthus(Eye folds)
• Feeding difficulties in infancy
• Gastroesophageal reflux(Acid reflux)
• High hypermetropia(Severe farsightedness)
• Low-set, posteriorly rotated ears
• Microcephaly(Abnormally small skull)
• Narrow mouth(Small mouth)
• Seizure
• Self-injurious behavior(Self-injurious behaviour)
• Stereotypy(Repetitive movements)
• Strabismus(Cross-eyed)

Diagnosis

Clinical tests may include Cytogenetics Tests

• Karyotyping
• FISH-interphase
• FISH-metaphase
• Fluorescence in situ hybridization (FISH)

Molecular Genetics Tests

• Detection of homozygosity
• Sequence analysis of the entire coding region
• Deletion/duplication analysis
• Targeted variant analysis
• Uniparental disomy study (UPD)

Treatment

There is no cure for this syndrome. Treatment depends on the symptoms, and may include rehabilitation/educational programs, antiepileptic medication, and standard treatment for heart, kidney, eye, hearing or bone problems.

NIH genetic and rare disease info

• NIH info on Chromosome 1p36 deletion syndrome

Chromosome 1p36 deletion syndrome is a rare disease.

Chromosome 1p36 deletion syndrome Resources
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