2q23.1 microdeletion syndrome

Alternate names

Del(2)(q23.1); Monosomy 2q23.1; Pseudo-Angelman syndrome; Chromosome 2q23.1 microdeletion syndrome

Twins in Poland with microdeletion syndrome of 22q11

Summary

2q23.1 microdeletion syndrome is a rare chromosome disorder. Symptoms may include seizures, moderate to severe learning problems, speech delays, behavior problems, trouble sleeping, and developmental delay (learn to crawl, sit or walk later than other babies). Children affected by 2q23.1 microdeletion syndrome may also have low muscle tone (hypotonia), slow weight gain, and may be shorter than family members.

Cause

• 2q23.1 microdeletion syndrome is caused by the loss of a small piece of one copy of chromosome 2, one of the 23 pairs of chromosomes in each cell in our body.
• Losing this small piece of chromosome 2 means that people with this microdeletion are missing one copy of the gene called MBD5.
• Most genes, including MBD5, act as a blueprint or code that tells a cell how to make a specific protein.
• When a gene is missing, the protein it codes for is also missing.
• Since only one copy of the MBD5 gene is missing, some MBD5 protein is made, but not enough.
• Medical researchers believe the MBD5 protein is a transcription regulator, which means it helps tell the cell which other genes should have their proteins made.
• These other proteins are thought to be important for the normal development and function of the brain.

Inheritance

• The mutation associated with 2q23.1 microdeletion syndrome generally is not passed down from the parents, but instead occurs for the first time in the affected child (de novo ).
• In many cases, therefore, there is no increased risk for other children of the couple to have 2q23.1 microdeletion syndrome.

• However, in some cases, a child has inherited the microdeletion from a parent in an autosomal dominant manner, but the parent does not have symptoms of 2q23.1 syndrome (unaffected) or is very mildly affected.
• This suggests the symptoms of 2q23.1 microdeletion syndrome may reduced penetrance.
• Therefore medical researchers recommend the chromosomes of both parents of child with 2q23.1 microdeletion syndrome are tested before talking to a genetic counselor about the risks of having another child with the microdeletion in future pregnancies.

Signs and symptoms

Symptoms may include seizures, moderate to severe learning problems, speech delays, behavior problems, trouble sleeping, and developmental delays (learn to crawl, sit or walk later than other babies). Children affected by 2q23.1 microdeletion syndrome may also have low muscle tone (hypotonia), slow weight gain, and may be shorter than family members.

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

• Delayed speech and language development(Deficiency of speech development)
• Intellectual disability, severe(Early and severe mental retardation)
• Seizure
• Stereotypy(Repetitive movements)

30%-79% of people have these symptoms

• Ataxia
• Brachycephaly(Short and broad skull)
• Broad forehead(Increased width of the forehead)
• Clinodactyly of the 5th finger(Permanent curving of the pinkie finger)
• Coarse facial features(Coarse facial appearance)
• Constipation
• Everted lower lip vermilion(Drooping lower lip)
• Generalized hirsutism(Excessive hairiness over body)
• Highly arched eyebrow(Arched eyebrows)
• Hyperactivity(More active than typical)
• Malar flattening(Zygomatic flattening)
• Microcephaly(Abnormally small skull)
• Muscular hypotonia(Low or weak muscle tone)
• Open mouth(Gaped jawed appearance)
• Paroxysmal bursts of laughter
• Polyphagia(Voracious appetite)
• Sandal gap(Gap between 1st and 2nd toes)
• Self-injurious behavior(Self-injurious behaviour)
• Short palm
• Short stature(Decreased body height)
• Sleep disturbance(Difficulty sleeping)
• Synophrys(Monobrow)
• Tented upper lip vermilion

5%-29% of people have these symptoms

• Cryptorchidism(Undescended testes)
• Hip dysplasia
• Hypoplasia of penis(Underdeveloped penis)
• Macrodontia(Increased width of tooth)

Diagnosis

Chromosome disorders may be suspected in people who have developmental delays, intellectual disabilities and/or physical abnormalities. Several types of genetic tests can identify chromosome disorders:

• Karyotyping
• Microarray (also called array CGH)
• Fluorescence in situ hybridization (FISH)

NIH genetic and rare disease info

• NIH info on 2q23.1 microdeletion syndrome

2q23.1 microdeletion syndrome is a rare disease.

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