Chromosome 2q37 Deletion Syndrome
Chromosome 2q37 Deletion Syndrome is a rare chromosomal disorder that can affect many body parts. It can develop when there is deletion of genetic material on chromosome 2 (from a specific locus (37) of the long arm (q) of chromosome 2), leading to a set of associated signs and symptoms.
What are the other Names for this Condition? (Also known as/Symptoms)
- Albright Hereditary Osteodystrophy Type 3
- Brachydactyly-Mental Retardation Syndrome
- Deletion 2q37-qter
What is Chromosome 2q37 Deletion Syndrome? (Definition/Background Information)
- Chromosome 2q37 Deletion Syndrome is a rare chromosomal disorder that can affect many body parts. It can develop when there is deletion of genetic material on chromosome 2 (from a specific locus (37) of the long arm (q) of chromosome 2), leading to a set of associated signs and symptoms
- The deletion may occur spontaneously or can be due to genetic phenomena such as unbalanced translocation and chromosome ring formation. Additionally, scientists believe that mutations in the HDAC4 gene, which codes for a histone deacteylase enzyme, may be responsible for this syndrome
- There are currently no risk factors associated with Chromosome 2q37 Deletion Syndrome. This chromosomal anomaly is usually known to develop from sporadic mutations (majority of cases). In a small percentage though, a family history of this condition is observed to be a risk factor. The condition is manifested at birth (congenital manifestation)
- Some of the main signs and symptoms of Chromosome 2q37 Deletion Syndrome include facial abnormalities, low muscle tone, feeding difficulties in newborn, congenital abnormalities in the heart and kidneys, problems with proper growth and development, intellectual disability, and autism spectrum disorders (ASD). The syndrome can lead to potential complications including seizures, heart defects, kidney malfunction, and short stature
- The management of the various symptoms associated with Chromosome 2q37 Deletion Syndrome may require the concerted effort by a team of healthcare specialists; with treatment being provided throughout the life of the affected individual. The treatment may include the use of hearing aids, speech and language therapy, physiotherapy, and surgery for correction of heart defects
- The prognosis is primarily dependent on the severity of the disorder, and it varies from one child to another. Many children with Chromosome 2q37 Deletion Syndrome are able to cope well through adequate treatment and supportive care. With prompt and continued care, the life span of an individual with this syndrome is reportedly not affected. Also, mild cases have better prognosis than individuals with severe conditions
Who gets Chromosome 2q37 Deletion Syndrome? (Age and Sex Distribution)
- Chromosome 2q37 Deletion Syndrome is a rare genetic disorder with a currently unknown prevalence. Only about 100 cases have so far been recorded in medical history
- In many cases, individuals with mild signs and symptoms may be undiagnosed in their lifetime. Hence, a true incidence of the disorder may be difficult to estimate
- The onset of symptoms associated with 2q37 Deletion Syndrome generally occurs at birth and evolves as the child grows and develops
- Both male and female genders can be affected
- No specific race or ethnic group is noted to have a higher risk for the condition
What are the Risk Factors for Chromosome 2q37 Deletion Syndrome? (Predisposing Factors)
In a vast majority of individuals, there are no identified risk factors for Chromosome 2q37 Deletion Syndrome.
- A positive family history is a relatively minor risk factor, since only 5% of the affected individuals are known to inherit 2q37 Deletion Syndrome
- Currently, no environmental and lifestyle (including dietary) factors have been implicated
- The syndrome is not caused by what the expectant mother does or does not do, either prior to or during pregnancy
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Chromosome 2q37 Deletion Syndrome? (Etiology)
Chromosome 2q37 Deletion Syndrome is caused by abnormalities in chromosome 2 as outlined below:
- Loss of genetic material from the long arm (q) of chromosome 2 at a specific locus (37), due to a spontaneous deletion
- This occurs during the formation of gametes (egg and sperm) or in the early fetal developmental stages
- The deletion frequently occurs in the end or terminal of the chromosome, and the loss of genetic material could vary from one affected individual to another
- The size of deletion could result in the loss of multiple genes, leading to the characteristic symptoms observed in individuals with
- Alteration in the structure of chromosome 2, owing to a phenomenon called “unbalanced translocation”, in the parents
- A parent carries gamete cells (egg or sperm) which have a chromosomal re-arrangement. There is exchange of parts between chromosome 2 and another chromosome, as a result of which there is no loss of genetic material in that individual. This is termed “balanced translocation”
- This is often the case with the inherited cases of the disorder
- Balanced translocations are not reported to cause serious health issues in the “balanced translocation carriers”
- Although, the balance could get lost in subsequent generations, in which case it is termed “unbalanced translocation”
- When the translocation becomes “unbalanced,” loss of genetic material occurs from chromosome 2, leading to the characteristic traits of Chromosome 2q37 Deletion Syndrome in the offspring
- In a minority of cases, chromosomal abnormalities such as ring formation may lead to the syndrome. For example, chromosome 2 may break at two places and the new ends might fuse to form a ring, and genetic material from the broken piece may be lost
- It has been reported that several individuals with a mutation in the HDAC4 gene (that codes for a class of enzymes known as histone deacetylases) exhibit symptoms of Chromosome 2q37 Deletion Syndrome, even without the deletion of genetic material. This has prompted scientists to propose that mutations in HDAC4 gene may cause the syndrome as well
It is important to note that a child’s development and future is not only influenced by the chromosome material duplicated/deleted and genes involved, but also by other factors such as one’s environment, involvement of other genes, and unique personality.
Additional (general) information on chromosomes, which is helpful in understanding the disorder:
Chromosomes are microscopic thread-like protein structures present in each cell nucleus that carry genetic information in the form of DNA (deoxyribonucleic acid). DNAs are nucleic acids that encodes the genetic information of any organisms; a basic unit of the DNA is termed a gene with a specific set of instructions and a defined function. Each chromosome is “X” shaped with a center, called the centromere, and two short arms (termed p arms) and two long arms (termed q arms).
Humans have 46 chromosomes in the cell nucleus, in 23 pairs, of which one pair is named the sex chromosome. In males, it is designated XY, for chromosome X and chromosome Y; while, in females, it is designated XX, for a pair of chromosome X. The other 22 pairs of chromosomes are numbered chromosome 1 through 22, approximately according to size (with chromosome 1 being the largest; chromosome 21 being the smallest) and are referred to as autosomes or somatic chromosomes. During conception, the embryo inherits one copy of each chromosome from each parent (i.e., mother and father). Any alteration in the chromosome numbers or structure, such as via addition or deletion of chromosomal material, can result in mild to severe genetic abnormalities that may manifest as birth defects, growth delays, and intellectual disabilities.
A chromosome deletion disorder indicates that a certain portion of the chromosomal material is missing, which may be detected through molecular genetic testing. Depending on the nature and amount of material deleted, the manifestation of a set of signs and symptoms are noted.
What are the Signs and Symptoms of Chromosome 2q37 Deletion Syndrome?
The signs and symptoms of Chromosome 2q37 Deletion Syndrome may be significantly different from one individual to another. The degree of signs and symptoms are often related to the amount of chromosome material deleted and the number of genes affected. As a general rule, a small loss of chromosome material generally results in milder signs and symptoms. Conversely, larger deletion of the chromosome material generally results in severe signs and symptoms. It is important to note that exceptions may also occur, where individuals with small amount of chromosomal loss, may have disproportionately severe presentations.
The characteristic signs and symptoms of Chromosome 2q37 Deletion Syndrome include:
- Hypotonia (or reduced muscle tone) in a majority of newborns with the condition
- Feeding difficulties
- Issues with the gastrointestinal tract, such as acid reflux
- Distinctive facial features that may include:
- Prominent forehead
- Scant hair
- Deep-set eyes, unnaturally arched eyebrows
- Flat and broad nasal bridge; thin upper lip
- Abnormal ears
- Skin folds
- Abnormally small fingers and toes (known as brachymetaphalangy)
- Hypermobility of joints
- Failure to achieve developmental milestones
- Short stature
- Intellectual disability
- Autism or autism spectrum disorders (that is noted in about 25% of affected individuals)
- Inflammatory skin conditions such as eczema
- Malformation of genitalia
Note: The type and severity of symptoms are reported to vary even in individuals with comparable deletions of genetic material from chromosome 2.
How is Chromosome 2q37 Deletion Syndrome Diagnosed?
Children can have varying signs and symptoms. Some children with mild signs and symptoms may go undiagnosed in their lifetimes. Given the rarity of the condition, the healthcare provider should have a high index of suspicion to consider Chromosome 2q37 Deletion Syndrome in the differential diagnosis. Often, specialized tests are necessary to confirm the disorder.
2q37 Deletion Syndrome is diagnosed on the basis of the following information:
- Complete physical examination and thorough medical history evaluation, including family medical history
- Assessment of the presenting signs and symptoms, including evaluation of body systems such as vision, hearing, muscles, heart, kidneys, central nervous system, genitalia, and immune system
- Hearing assessment through various tests including:
- Otoscopy: Examination using an instrument that allows the physician to look inside the ear
- Weber test: A test in which a vibrating tuning fork is placed on the midline of the head
- Rinne test: A test in which a vibrating tuning fork is held next to the ear and then in front of the ear, until the individual no longer hears the sound
- Audiometric test: Hearing tests that involve listening to different tones
- Tympanometry: A test that puts air pressure in the ear canal in order to move the eardrum, and then measures the eardrum mobility (movement)
- Evaluation of heart defects through:
- Chest X-rays
- Electrocardiogram (EKG)
- Cardiac catheterization
- Fetal ultrasound for heart defects
- Laboratory tests, as needed, such as electrolyte levels, serum calcium levels, thyroid function test, kidney function test, urine tests, sex hormone studies, etc.
- Radiological studies of the affected regions, as needed
- Brain scans (to determine corpus callosum): These may include prenatal ultrasounds and MRI scans, and CT/MRI scans after development of the child
- Neurological examination that involves the central nervous system (brain and spinal cord); to evaluate psychomotor and cognitive skills
- Electroencephalogram (EEG) for monitoring seizures
- Checking kidneys for malformation and/or malfunction
- Behavioral studies
- Prenatal studies including abdominal ultrasonography
- Specialized genetic testing techniques are often required to confirm the diagnosis. This may include:
- Fluorescence in situ hybridization (FISH) testing
- Array comparative genomic hybridization (array-CGH)
- DNA sequencing
Often, karyotyping of the chromosome is not adequate to diagnose the condition, since individuals with this condition can have normal karyotype chromosomal studies.
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Chromosome 2q37 Deletion Syndrome?
Some potential complications from Chromosome 2q37 Deletion Syndrome include:
- Severe emotional stress for parents and caregivers
- Pregnancy complications
- Delayed milestone achievements
- Development of Wilms tumor, which is a rare form of kidney cancer
- Congenital heart disease
- Scoliosis (curvature in spine)
- Central nervous system abnormalities, including brain malformation
- Seizures, which can result in fall injuries
- Heart, kidney, and genitourinary tract defects that may be severe
- Lack of intellectual development
- Reduced quality of life
Complications may occur with or without treatment, and in some cases, due to treatment also.
How is Chromosome 2q37 Deletion Syndrome Treated?
There is no cure for Chromosome 2q37 Deletion Syndrome since it is a genetic condition. The treatment is usually given to manage the signs and symptoms and any complication that develops. It also depends on the severity of the signs and symptoms and the body systems affected. Individuals with mild signs and symptoms may require periodic monitoring without significant medical intervention. Often, a multidisciplinary team of specialists including pediatricians, otolaryngologists, neurologists, internists, cardiologists, endocrinologists, surgeons, and other healthcare professionals are involved in managing the condition.
The treatment measures for 2q37 Deletion Syndrome may involve:
- Use of hearing aids
- Seizure control using anticonvulsant medication, vitamin supplements, and ketogenic diet: Seizure control is important to ensure that the child’s learning ability is not significantly affected
- Employing learning strategies via music therapy, visual and tactile books, learning through fun and play, and lots of repetition. Children are known to like music and singing. Writing by holding a pencil may be very difficult; but touchscreen computers and keyboards are known to be easier to use and learn
- Speech and language therapy; the use of sign language may be beneficial; rectification of hearing impairment may improve speech and language development
- Physiotherapy for weakened muscles, including incorporating daily exercise regimen
- Development of motor skills via daily exercises, swimming, hydrotherapy, and other adapted activities; use of specially-designed toys and daily-used items (such as spoons and cups)
- Use of walking aids including foot orthotics and special footwear and shoe inserts; wheelchair assistance may be necessary
- For feeding difficulties, use of feeding tubes (temporary nasogastric or gastrostomy tubes), medications, feed thickeners, bottle-feeding expressed milk, including special diets and nutritional supplements
- Heart abnormalities may require surgical correction in some cases, whereas some defects may improve over time without the need for any invasive procedures
- Surgical correction of physical defects, as assessed by a healthcare expert
- Use of padded brace for abnormal spinal curvature and posture management, including surgical correction of severe cases. Also, children may be provided specially designed furniture, such as chairs, tables, and beds, for spine support while sitting and sleeping
- For eczema, the treatment may involve the use of moisturizing creams and emollients and steroid creams as necessary; many children overcome the condition as they get older
- Psychotherapy, behavior modification, and establishing discipline techniques, as necessary
- Occupational therapy
Undertaking monitoring of symptoms as they evolve and providing with supportive care is important. Routine physical activity may be recommended to address obesity issues.
How can Chromosome 2q37 Deletion Syndrome be Prevented?
Chromosome 2q37 Deletion Syndrome may not be preventable since many of these genetic disorders are diagnosed at or following the birth of the child. A majority of cases are sporadic occurrences, which means there is no family history of the condition.
In some rare cases, the condition may be familial, meaning they occur within families. In expecting parents with a familial history:
- Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
- If there is a family history of the condition, then genetic counseling will help assess risks before planning for a child
- Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as 2q37 Deletion Syndrome
It is important to note that the chances of both the parents with normal chromosomes having another child with Chromosome 2q37 Deletion Syndrome is highly unlikely. This may be confirmed via specialized prenatal testing and preimplantation genetic diagnosis (PGD), if needed. Prenatal tests may include chorionic villus sampling (CVS) and amniocentesis.
What is the Prognosis of Chromosome 2q37 Deletion Syndrome? (Outcome/Resolutions)
The prognosis of Chromosome 2q37 Deletion Syndrome depends on the congenital defects and malformations observed in the individual. It depends upon the severity of the signs and symptoms; those with mild symptoms have better outcomes than those with severe symptoms.
- Children with mild conditions (usually from small deletions) are generally able to cope well via appropriate treatment and adaptive behaviors as they get older
- Children usually require lifelong medical support and care; it may also take some children a long time (several years) to gain a measure of independence
- It has been reported that the lifespan is not compromised, if continued care is provided
Additional and Relevant Useful Information for Chromosome 2q37 Deletion Syndrome:
Please visit our Congenital & Genetic Disorders Health Center for more physician-approved health information:
What are some Useful Resources for Additional Information?
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126 Gaithersburg, MD 20898-8126
Toll-Free: (888) 205-2311
TTY: (888) 205-3223
International Telephone Access Number: (301) 251-4925
Fax: (301) 251-4911
National Organization for Rare Disorders (NORD)
55 Kenosia Avenue Danbury, CT 06810
Phone: (203) 744-0100
Toll-Free: (800) 999-6673
Fax: (203) 798-2291
Chromosome Disorder Outreach (CDO)
PO Box 724, Boca Raton FL 33429-0724
Phone: (561) 395-4252 (Family Helpline)
Unique – Rare Chromosome Disorder Support Group
G1, The Stables, Station Road West
Surrey, RH8 9EE, United Kingdom
Phone: +44 (0)1883 723356
References and Information Sources used for the Article:
https://ghr.nlm.nih.gov/condition/2q37-deletion-syndrome (accessed on 08/31/2021)
http://www.ncbi.nlm.nih.gov/books/NBK1158/ (accessed on 08/31/2021)
http://www.rarechromo.org/information/Chromosome%20%202/2q37%20deletion%20syndrome%20FTNW.pdf (accessed on 08/31/2021)
http://www.orpha.net/consor4.01/www/cgi-bin/OC_Exp.php?lng=EN&Expert=1001 (accessed on 08/31/2021)
https://www.genome.gov/about-genomics/fact-sheets/Chromosomes-Fact-Sheet (accessed on 08/31/2021)
https://www.cdc.gov/genomics/about/basics.htm (accessed on 08/31/2021)
Helpful Peer-Reviewed Medical Articles:
Leroy, C., Landais, E., Briault, S., David, A., Tassy, O., Gruchy, N., ... & Lacombe, D. (2013). The 2q37-deletion syndrome: an update of the clinical spectrum including overweight, brachydactyly and behavioural features in 14 new patients. European Journal of Human Genetics, 21(6), 602-612.
Pagon, R. A., Adam, M. P., Ardinger, H. H., Bird, T. D., Dolan, C. R., Fong, C. T., ... & Lacbawan, F. (2013). 2q37 Microdeletion Syndrome.
Sakai, Y., Souzaki, R., Yamamoto, H., Matsushita, Y., Nagata, H., Ishizaki, Y., ... & Hara, T. (2014). Testicular sex cord-stromal tumor in a boy with 2q37 deletion syndrome. BMC medical genomics, 7(1), 19.
Jones, K. L., Jones, M. C., & Del Campo, M. (2013). Smith's recognizable patterns of human malformation. Elsevier Health Sciences.
Geng, Q., Xie, J. S., Wu, W. Q., Luo, F. W., & Chen, W. B. (2013). [One case of 2q37 deletion syndrome: clinical and genetic diagnosis]. Zhonghua er ke za zhi. Chinese journal of pediatrics, 51(12), 934-937.
Villavicencio-Lorini, P., Klopocki, E., Trimborn, M., Koll, R., Mundlos, S., & Horn, D. (2013). Phenotypic variant of Brachydactyly-mental retardation syndrome in a family with an inherited interstitial 2q37. 3 microdeletion including HDAC4. European Journal of Human Genetics, 21(7), 743-748.
Spielmann, M., Marx, S., Barbi, G., Flöttmann, R., Kehrer‐Sawatzki, H., König, R., ... & Borck, G. (2016). Femoral facial syndrome associated with a de novo complex chromosome 2q37 rearrangement. American Journal of Medical Genetics Part A.
Coca–Pelaz, A., Llorente–Pendás, J. L., García–Martínez, J., Vivanco–Allende, B., Balbín, M., Suárez, C., & Hermsen, M. (2013). Medullary thyroid carcinoma and 2q37 deletion in a patient with nevoid basal cell carcinoma syndrome: Clinical description and genetic analysis. Head & neck, 35(5), E147-E152.