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

• 3q29 Deletions and Microdeletions Syndrome

What is Chromosome 3q29 Deletions and Microdeletions Syndrome? (Definition/Background Information)

• Chromosome 3q29 Deletions and Microdeletions Syndrome is a rare chromosomal disorder that develops when there is missing genetic material on chromosome 3 leading to a set of associated signs and symptoms. These may be mild or severe, depending on several factors such as the amount of genetic material lost. The condition affects newborn children (congenital manifestation)
• Many children and adults are typically healthy presenting no major birth defects. However, in others, it can result in low birth weight, developmental delays, poor motor skills, facial abnormalities, seizures, and hearing impairment. Chromosome 3q29 Deletions and Microdeletions Syndrome may present complications such as failure to thrive, delayed achievement of milestones, autism, and a reduced quality of life
• This chromosomal anomaly may develop from sporadic mutations (majority of cases), or it may be inherited from one’s parents (very rarely). 3q29 Deletions and Microdeletions Syndrome may be diagnosed through specialized genetic testing. In some children, the condition may be mild and hence can also remain undiagnosed
• Following a diagnosis, the condition may be managed based on the presenting symptoms and extent of involvement of the body systems. The treatment may involve physician experts from several specialties, and can include the use of speech and learning assistance, hearing aids, seizure control, physiotherapy, and surgery for correction of abnormalities
• The prognosis is primarily dependent on the severity of the disorder, and it varies from one child to another. Many children with Chromosome 3q29 Deletions and Microdeletions Syndrome are able to cope well through adequate treatment and supportive care. Some of the signs and symptoms associated with the condition are known to improve with time

Who gets Chromosome 3q29 Deletions and Microdeletions Syndrome? (Age and Sex Distribution)

• Chromosome 3q29 Deletions and Microdeletions Syndrome is an extremely rare congenital disorder. Only a few cases (less than 50) have been reported in the medical literature
• 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 presentation of symptoms may occur at or following the birth
• 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 3q29 Deletions and Microdeletions Syndrome? (Predisposing Factors)

In a vast majority of individuals, there are no identified risk factors for Chromosome 3q29 Deletions and Microdeletions Syndrome.

• In some individuals, a positive family history may be an important risk factor for 3q29 Deletions and Microdeletions 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 3q29 Deletions and Microdeletions Syndrome? (Etiology)

Chromosome 3q29 Deletions and Microdeletions Syndrome is caused by deletion of genetic material from the short arm (p) of chromosome 3 at band q29; the amount of missing chromosome material varies widely from one individual to another resulting in a variable set of signs and symptoms.

There are two chromosomes numbered 3. Children with 3q29 Deletions and Microdeletions Syndrome typically will have one (chromosome 3) in normal condition, while the other is abnormal. The abnormality is characterized by a loss of chromosomal material. The q29 band on chromosome 3 is known to house around 20 genes.

• Most cases of the disorder develop sporadically (de novo) during embryonic development. This means that no deletion of genetic material at 3p26 is observed in either of the parents. However, in rare cases, Chromosome 3q29 Deletions and Microdeletions Syndrome may be inherited
• The chromosomal abnormality is termed a deletion when the deleted part is large enough to be visible under a microscope with normal magnification. However, in microdeletion, a very tiny part of the chromosome is lost or missing, and it is not even visible under a microscope with high magnification. In such cases, multiplex ligation-dependent probe amplification (MLPA), cytogenetic fluorescent in situ hybridization (FISH), or array comparative genomic hybridization (array-CGH) studies may be necessary to detect the deletions

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 3q29 Deletions and Microdeletions Syndrome?

The signs and symptoms of Chromosome 3q29 Deletions and Microdeletions 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 missing/lost, how much deletion has occurred (quantity), where the deletions occur, and if the involvement of other chromosomes are noted.

The commonly noted signs and symptoms of 3q29 Deletions and Microdeletions Syndrome include:

• Poor muscle tone (hypotonia) causing motor delays that can be mild or severe, and include:
  • Feeding problems leading to small and underweight children
  • Difficulty in holding small items such as a cup or spoon
  • Drawing and writing difficulties
  • Difficulty in climbing stairs and difficulty in sitting without support
  • Standing and walking difficulties; unsteady walk
  • Help needed for wearing clothes and undressing
• Some feeding difficulties due to sucking and swallowing difficulties, vomiting, and gastroesophageal reflux disease
• Presence of abnormal hands and feet (such as slender long fingers, inwards curved toes, webbing between the toes, etc.)
• Poor gross motor skills; fine motor skills are usually good
• Seizures may be observed in infants and young children
• Mild or severe eczema that may get worse during summers
• Breathing issues in some children
• Hearing impairment that mostly develops from glue ear (fluid buildup in middle ear)
• Heart abnormalities can result in associated signs and symptoms, such as chest pain, shortness of breath, dizziness, fainting, palpitations, and tiredness, among others. The following heart abnormalities are noted:
  • Valve defects, such as atrial septal defects (ASD), is usually present at birth
  • Structural defects such as patent ductus arteriosus (PDA) (most common heart defect)
• Speech and learning disabilities; speech skills may be somewhat affected
• Minor genital abnormalities, which mostly affect boys:
  • Cryptorchidism (undescended testes)
  • Hypospadias
  • Abnormally-located penis
• Inguinal hernias
• Teeth abnormalities in some children, including widely spaced teeth
• Distinctive facial features may include prominent forehead; small-sized head (in nearly 50% of the cases); long, narrow face, eyes that slant somewhat downwards, large ears, a prominent bridge to the nose, which is typically long with a broad tip, a short philtrum - some features improve change over time
• Behavioral problems

Major birth defects are not usually noted, and children (and adults) are healthy in most cases; life expectancy is also reported as being mostly normal.

How is Chromosome 3q29 Deletions and Microdeletions 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 1q4 Deletions in the differential diagnosis. Often, specialized tests are necessary to confirm the disorder.

Chromosome 3q29 Deletions and Microdeletions 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
• Kidney and urinary tract scans
• 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)
• 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 3q29 Deletions and Microdeletions Syndrome?

The complications of Chromosome 3q29 Deletions and Microdeletions Syndrome may include:

• Severe emotional stress for parents and caregivers
• Pregnancy complications
• Intrauterine growth retardation (IUGR); some babies are underweight at birth
• Failure to thrive
• Delayed milestone achievement in about 50% of the cases; especially, for a child to sit, stand, or walk
• Sleep (infantile) apnea may be associated with seizures (night-time seizures)
• Poor growth due to malnutrition caused by weak suckling
• Spinal curve abnormalities, such as scoliosis, which may be mild or severe
• Risk of falls and injury due to seizures
• Deafness
• Recurrent ear infections; there is also a risk for pneumonia from frequent ear infections
• Severe heart anomalies
• Moderate to severe cognitive impairment; low IQ levels
• Reduced quality of life

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

How is Chromosome 3q29 Deletions and Microdeletions Syndrome Treated?

There is no cure for Chromosome 3q29 Deletions and Microdeletions 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 Chromosome 3q29 Deletions and Microdeletions Syndrome may involve:

• Use of hearing aids and cochlear implants; in case of fluid buildup in the middle ear, some children may require the placement of a small ventilation tubes to help with improved fluid drainage
• 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 suitable learning strategies via music therapy, visual and tactile books, learning through fun and play, and lots of repetition. 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)
• 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; some defects tend to improve over time without 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
• Surgical correction (orchiopexy) of undescended testicles and other genital defects
• Sleep disorders may require medication; daytime naps may be advised
• 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
• Hernia repair surgery for inguinal hernias, as needed
• Psychotherapy, behavior modification, and establishing discipline techniques, as necessary
• Social skills training support groups and exercises
• Occupational therapy

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

How can Chromosome 3q29 Deletions and Microdeletions Syndrome be Prevented?

Chromosome 3q29 Deletions and Microdeletions 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 (chromosome) testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy), if available, 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 3q29 Deletions and Microdeletions 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 3q29 Deletions and Microdeletions Syndrome? (Outcomes/Resolutions)

The prognosis of Chromosome 3q29 Deletions and Microdeletions Syndrome is dependent upon the severity of the signs and symptoms and associated complications, if any. It may be assessed on a case-by-case basis.

• Children with mild conditions (usually from small deletions) are generally able to cope well via appropriate treatment and adaptive behaviors as they get older
• In a majority of individuals, the condition is reportedly mild with few to no birth defects observed. In such individuals, the life expectancy is also normal
• Rarely, some children may require extended medical support and care

Additional and Relevant Useful Information for Chromosome 3q29 Deletions and Microdeletions Syndrome:

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

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