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Disease Profile

2q23.1 microdeletion syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

<1 / 1 000 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

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


Chromosome Disorders; Congenital and Genetic Diseases; Nervous System Diseases


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 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.

2q23.1 deletion syndrome is caused by the loss of a small piece of DNA in one copy of chromosome 2, one of the 23 pairs of chromosomes in each cell in our bodies. Most cases of 2q23.1 deletion syndrome are de novo, which means the deletion was not passed down from either parent.

Diagnosis of 2q23.1 microdeletion syndrome may be suspected by symptoms but is confirmed by genetic testing. Treatment is based on the signs and symptoms of each person and may include seizure medication, speech therapy, behavior therapy, physical, and occupational therapy, and special education programs.[1][2][3] 


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Delayed speech and language development
Deficiency of speech development
Delayed language development
Delayed speech
Delayed speech acquisition
Delayed speech development
Impaired speech and language development
Impaired speech development
Language delay
Language delayed
Language development deficit
Late-onset speech development
Poor language development
Speech and language delay
Speech and language difficulties
Speech delay

[ more ]

Intellectual disability, severe
Early and severe mental retardation
Mental retardation, severe
Severe mental retardation

[ more ]

Repetitive movements
Repetitive or self-injurious behavior

[ more ]

30%-79% of people have these symptoms
Short and broad skull
Broad forehead
Increased width of the forehead
Wide forehead

[ more ]

Clinodactyly of the 5th finger
Permanent curving of the pinkie finger
Coarse facial features
Coarse facial appearance
Everted lower lip vermilion
Drooping lower lip
Outward turned lower lip

[ more ]

Generalized hirsutism
Excessive hairiness over body
Highly arched eyebrow
Arched eyebrows
Broad, arched eyebrows
High, rounded eyebrows
High-arched eyebrows
Thick, flared eyebrows

[ more ]

More active than typical
Malar flattening
Zygomatic flattening
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference

[ more ]

Muscular hypotonia
Low or weak muscle tone
Open mouth
Gaped jawed appearance
Gaped mouthed appearance
Slack jawed appearance

[ more ]

Paroxysmal bursts of laughter
Voracious appetite
Sandal gap
Gap between 1st and 2nd toes
Gap between first and second toe
Increased space between first and second toes
Sandal gap between first and second toes
Wide space between 1st, 2nd toes
Wide space between first and second toes
Wide-spaced big toe
Widely spaced 1st-2nd toes
Widely spaced first and second toes
Widened gap 1st-2nd toes
Widened gap first and second toe

[ more ]

Self-injurious behavior
Self-injurious behaviour
Short palm
Short stature
Decreased body height
Small stature

[ more ]

Sleep disturbance
Difficulty sleeping
Trouble sleeping

[ more ]


[ more ]

Tented upper lip vermilion
5%-29% of people have these symptoms
Undescended testes
Undescended testis

[ more ]

Hip dysplasia
Hypoplasia of penis
Underdeveloped penis
Increased width of tooth


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.[4][5]



Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • Orphanet lists international laboratories offering diagnostic testing for this condition.


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • Unique is a source of information and support for families and individuals affected by rare chromosome disorders. Click on the link to view information about 2q23.1 microdeletion syndrome.

        In-Depth Information

        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) lists the subtypes and associated genes for 2q23.1 microdeletion syndrome in a table called Phenotypic Series. Each entry in OMIM includes a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss 2q23.1 microdeletion syndrome. Click on the link to view a sample search on this topic.


          1. Dr Sarah Elsea. 2q23.1 microdeletion syndrome. Unique; 2013; https://www.rarechromo.org/information/Chromosome%20%202/2q23.1%20microdeletion%20syndrome%20FTNW.pdf.
          2. Dr Nicole Morichon-Delvallez. 2q23.1 microdeletion syndrome. Orphanet; May 2010; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=228402.
          3. Victor A. McKusick, Ada Hamosh. Mental Retardation, Autosomal Dominant 1; MRD1. Online Mendelian Inheritance in Man; January 11, 2016; https://www.omim.org/entry/156200.
          4. Céline Bonnet, Asma Ali Khan, Emmanuel Bresso, Charlène Vigouroux, Mylène Béri, Sarah Lejczak, Bénédicte Deemer, Joris Andrieux, Christophe Philippe, Anne Moncla, Irina Giurgea, Marie-Dominique Devignes, Bruno Leheup, and Philippe Jonveaux. Extended spectrum of MBD5 mutations in neurodevelopmental disorders. European Journal of Human Genetics. February 20, 2013; 21(12):1457-1461. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3831065/.
          5. Mullegama SV, Elsea SH. Clinical and Molecular Aspects of MBD5-Associated Neurodevelopmental Disorder (MAND). Journal of Human Genetics. August 2016; 24(9):1235-1243. https://www.ncbi.nlm.nih.gov/pubmed/27222293.

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