Chromosome 3p- syndrome

Alternate names

Del(3p) syndrome; Chromosome 3, monosomy 3p25; Deletion 3p25; Chromosome 3pter-p25 Deletion Syndrome; Telomeric monosomy 3p; Distal 3p deletion; 3p- syndrome; Distal monosomy 3p; Monosomy 3pter

Definition

Chromosome 3p- syndrome is a rare chromosome abnormality that occurs when there is a missing copy of the genetic material located towards the end of the short arm (p) of chromosome 3.

Cause

• In most people with chromosome 3p- syndrome, the deletion occurs as a new mutation (called a de novo mutation) and is not inherited from a parent.
• De novo mutations are due to a random error that occurs during the formation of egg or sperm cells, or shortly after conception.
• In a few cases, the deletion is inherited from a parent.

Inheritance

• In most cases, chromosome 3p- syndrome occurs for the first time in the affected person (de novo mutation).
• However, the deletion is rarely inherited from a parent.
• In these cases, the deletion is passed down in an autosomal dominant manner.
• This means that a person with chromosome 3p- syndrome has a 50% chance with each pregnancy of passing the condition on to his or her child.
• People interested in learning more about genetic risks to themselves or family members should speak with a genetics professional.
• In theory, it is possible for a parent to not have the deletion in their chromosomes on a blood test, but have the deletion in some of their egg or sperm cells only.
• This phenomenon is called germline mosaicism.
• In these rare cases, it would be possible to have another child with the deletion.
• To our knowledge, this has not been reported with chromosome 3p- syndrome.

Signs and symptoms

The signs and symptoms of chromosome 3p- syndrome and the severity of the condition depend on the exact size and location of the deletion and which genes are involved. Some affected people appear to have no features or mild features, while others are more severely affected.

Common symptoms shared by many people with this condition include:

• Growth problems both before and after birth
• Feeding difficulties
• Developmental delay
• Poor muscle tone (hypotonia)
• Intellectual disability
• Ptosis
• Distinctive facial features
• Microcephaly and/or unusual head shape
• Autism spectrum disorder

Other features that may be seen include cleft palate; extra fingers and/or toes; gastrointestinal abnormalities; seizures; hearing impairment; kidney problems; and/or congenital heart defects.

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

• Cognitive impairment(Abnormality of cognition)
• [[Hypertelorism](Wide-set eyes)
• Long philtrum
• Micrognathia(Little lower jaw)
• Ptosis(Drooping upper eyelid)
• Short stature(Decreased body height)
• Telecanthus(Corners of eye widely separated)

30%-79% of people have these symptoms

• Atrioventricular canal defect
• Brachycephaly(Short and broad skull)
• Cleft palate(Cleft roof of mouth)
• Cryptorchidism(Undescended testes)
• Downturned corners of mouth(Downturned corners of the mouth)
• Epicanthus(Eye folds)
• Hearing impairment(Deafness)
• High palate(Elevated palate)
• Intrauterine growth retardation(Prenatal growth deficiency)
• Low-set, posteriorly rotated ears
• Microcephaly(Abnormally small skull)
• Muscular hypotonia(Low or weak muscle tone)
• Postaxial hand polydactyly(Extra little finger)

5%-29% of people have these symptoms

• Abnormal renal morphology(Abnormally shaped kidney)
• Abnormal vestibulo-ocular reflex
• Anteverted nares(Nasal tip, upturned)
• Blepharophimosis(Narrow opening between the eyelids)
• Clinodactyly of the 5th finger(Permanent curving of the pinkie finger)
• Inguinal hernia
• Macular hypoplasia
• Preauricular pit(Pit in front of the ear)
• Prominent nasal bridge(Elevated nasal bridge)
• Sacral dimple(Spinal dimple)
• Seizure
• Short neck(Decreased length of neck)
• Spasticity(Involuntary muscle stiffness, contraction, or spasm)
• Thin vermilion border(Decreased volume of lip)
• Triangular face(Face with broad temples and narrow chin)
• Umbilical hernia
• Ventriculomegaly

Diagnosis

There are several different specialized tests that can be used to diagnose a chromosome 3p- syndrome. These include:

• Karyotype - a karyotype is a laboratory test that produces an image of a person's chromosomes. This test can be used to diagnose large deletions.
• FISH - a laboratory technique that is used to detect and locate a specific DNA sequence on a chromosome.
• During FISH, a chromosome is exposed to a small DNA sequence called a probe that has a fluorescent molecule attached to it. The probe sequence binds to its corresponding sequence on the chromosome.

This test can be used in combination with karyotyping for deletions that are too small to be seen on karyotype, alone. However, FISH is only useful if the person ordering the test suspects there is a duplication of a specific region of 3p.

• Array CGH - a technology that detects deletions that are too small to be seen on karyotype.

Treatment

• Because chromosome 3p- syndrome affects many different systems of the body, medical management is often provided by a team of doctors and other healthcare professionals.
• Treatment for this deletion varies based on the signs and symptoms present in each person.
• For example, children with delayed motor milestones (i.e. walking) and/or muscle problems may be referred for physical or occupational therapy.
• Severe feeding difficulties may be treated temporarily with a nasogastric tube or a gastrostomy tube to ensure that a baby or child gets enough nutrients.
• Certain medications may be prescribed to treat seizures.
• Special education services are often necessary for children with intellectual disability.
• Surgery may be required to treat certain physical abnormalities such as cleft palate or congenital heart defects, if present.

Prognosis

• The long-term outlook (prognosis) for people with chromosome 3p- syndrome varies from person to person.
• The severity of the condition and the associated signs and symptoms largely depend on the size and location of the deletion and the genes involved.

NIH genetic and rare disease info

• NIH info on Chromosome 3p- syndrome

Chromosome 3p- syndrome is a rare disease.

Chromosome 3p- syndrome Resources
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