What are the other Names for this Condition? (Also known as/Synonyms)

• 20p Deletion Syndrome
• Monosomy 20p Syndrome
• Partial Monosomy 20p Syndrome

What is Chromosome 20p Deletion Syndrome? (Definition/Background Information)

• Chromosome 20p Deletion Syndrome is a chromosome abnormality that occurs when there is a missing copy of the genetic material located on the short arm (p) of chromosome 20. The severity of the condition and the signs and symptoms depend on the size and location of the deletion and which genes are involved
• Features that often occur in people with chromosome 20p deletion include growth and developmental delay, mental health issues, and abnormal facial features. This chromosomal anomaly may develop from sporadic mutations (in a majority of cases), or it may be inherited from one’s parents (in rare cases). 20p Deletion Syndrome may be diagnosed through specialized genetic testing
• Following a diagnosis, the condition may be managed based on the presenting symptoms and extent of involvement of the body systems. The treatment of Chromosome 20p Deletion Syndrome may involve physician experts from several specialties, and can include the use of vision and hearing aids, physiotherapy, and surgery for correction of physical defects
• The prognosis is primarily dependent on the severity of the disorder, and it varies from one child to another. Many children with Chromosome 20p Deletion Syndrome are able to cope well through adequate treatment and supportive care. Some of the abnormalities are known to improve with time

Who gets Chromosome 20p Deletion Syndrome? (Age and Sex Distribution)

• Chromosome 20p Deletion Syndrome is a rare congenital disorder. The presentation of symptoms may occur at birth or following the birth of the child
• 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
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Chromosome 20p Deletion Syndrome? (Predisposing Factors)

In a vast majority of individuals, there are no identified risk factors for Chromosome 20p Deletion Syndrome.

• A positive family history may be an important risk factor, since 20p Deletion Syndrome can be inherited
• 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 20p Deletion Syndrome? (Etiology)

• In a majority of cases, Chromosome 20p Deletion Syndrome may be caused by a de-novo deletion of genetic material in the short arm (p) of chromosome 20
• Heritable changes passed from a parent with Chromosome 20p Deletion in which a subsequent chromosomal re-arrangement has led to a balanced translocation (in rare cases). If the chromosomal re-arrangement does not result in a net gain or loss of genetic material, it is known as a “balanced translocation”
• Individuals with balanced translocation of 20p deletion can have abnormalities in the development of egg or sperm, causing the disorder in their offspring
• Chromosome 20 is among the smallest of the chromosomes, and it houses around 740 genes, per current research. The deletions may be termed proximal or distal

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 20p Deletion Syndrome?

The signs and symptoms of Chromosome 20p 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 associated signs and symptoms depend on what material is deleted, how much deletion has occurred (quantity), where the deletion occurs (such as at the tip or center of the chromosome), and if the involvement of another chromosome is noted (known to occur in some cases).

The commonly noted signs and symptoms of 20p Deletion Syndrome include:

• Developmental delays to a certain small extent
• Feeding difficulties due to swallowing difficulties, vomiting, and gastroesophageal reflux disease
• Hearing impairment
• Small hands and feet; flatfeet
• Poor muscle tone (hypotonia) causing motor delays that can be mild or severe
• Difficulty in climbing stairs and difficulty in sitting without support
• Standing and walking difficulties
• Seizures in infants and children
• Heart abnormalities that can result in associated signs and symptoms, such as chest pain, shortness of breath, dizziness, fainting, palpitations, and tiredness, among others
• Speech and learning disabilities may be mild
• Distinctive facial features may include a small head with a long face, prominent forehead, coarse hair, deep set eyes, small mouth, overfolded outer edge of the ear, and large earlobes
• Underdeveloped genitalia especially in boys
• Behavioral problems

How is Chromosome 20p 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 20p Deletion Syndrome in the differential diagnosis. Often, specialized tests are necessary to confirm the disorder.

20p 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
  • Echocardiogram
  • 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
• Neurological examination that involves the central nervous system (brain and spinal cord)
• 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 20p Deletion Syndrome?

The complications of Chromosome 20p Deletion Syndrome may include:

• Severe emotional stress for parents and caregivers
• Delayed milestone achievement
• Hearing loss that may be partial or complete
• Poor growth due to malnutrition caused by weak suckling
• Short stature
• Frequent upper and lower respiratory infections in some cases
• Spinal curve abnormalities, such as scoliosis and kyphosis, which mostly develops from hypotonia
• Kidney defects; abnormally developed kidneys
• Severe intellectual deficiency
• Inappropriate or violent behavior
• Physical abnormalities that can cause difficulties in day-to-day living
• Lack of social skills
• Severe heart anomalies
• Reduced quality of life

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Chromosome 20p Deletion Syndrome Treated?

There is no cure for Chromosome 20p 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, ophthalmologists, otolaryngologists, neurologists, internists, cardiologists, endocrinologists, surgeons, and other healthcare professionals are involved in managing the condition.

The treatment measures for 20p Deletion Syndrome may involve:

• Use of hearing aids and cochlear implants
• 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, touch screen computers, etc.
• Speech and language therapy; the use of sign language may be beneficial
• Physiotherapy for weakened muscles, including incorporating daily exercise regimen
• Development of motor skills via daily exercises, swimming, 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
• For feeding difficulties, use of feeding tubes (temporary), medications, feed thickeners, including special diets and nutritional supplements
• Severe constipation may require dietary changes, including increased intake of fiber and wholegrains, along-with the administration of laxatives
• Heart abnormalities may require surgical correction in some cases; some defects tend to improve over time, sometimes within a year
• 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
• Surgical correction of genital defects
• Psychotherapy, behavior modification, and establishing discipline techniques, as necessary
• Occupational therapy

Regular medical screening at periodic intervals with tests and physical examinations are necessary and highly recommended.

How can Chromosome 20p Deletion Syndrome be Prevented?

Chromosome 20p 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

It is important to note that the chances of both the parents with normal chromosomes having another child with 20p 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 20p Deletion Syndrome? (Outcomes/Resolutions)

The prognosis of Chromosome 20p Deletion Syndrome is dependent upon the severity of the signs and symptoms and associated complications, if any.

• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• In many cases, children require lifelong medical support and care
• The long-term outlook may vary from one individual to another

Additional and Relevant Useful Information for Chromosome 20p Deletion Syndrome:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/