As humans, we all should share 23 chromosomes from each parent, for a total of 46. But what happens when some of the genetic material (genes made from DNA) in the chromosomes is missing? The outcome depends on the functions that the genetic material control.
Unfortunately, in a relatively newly identified problem, 1p36 deletion syndrome, (first deletion noted in 1981 and in 1997, the clinical features first outlined), a small segment of missing DNA results in large problems for individuals missing the DNA and for their families.
The name of the problem is 1p36 deletion syndrome. This numeric name means that it affects chromosome # 1, the largest human chromosome.
It precisely affects the area on the #1 chromosome that is on a short arm of the chromosome (p means the short arm above the centromere that joins the two parental copies of chromosome 1, and area 36 is where the missing DNA should be located).
In recent years (about 2005-08), recent diagnostic tests known as fluorescent in situ hybridization (FISH) and microarray comparative genomic hybridization (array CGH) have been developed to definitively diagnose the 1p36 deletion syndrome. CGH may determine about how much DNA is missing.
Characteristics of 1p36 Deletion Syndrome
- Low muscle tone (congenital hypotonia): Infants with 1p36 Deletion Syndrome often have low muscle tone, which may make it difficult for a newborn to suck and swallow.
Hypotonia may also delay sitting, crawling and walking. Muscle tone often improves with age and with physical therapy.
- Seizure disorder: Individuals with 1p36 Deletion Syndrome may have different types of seizures. Most seizure disorders can be controlled with medication.
- Growth/feeding problems: Infants with this condition often have difficulty gaining weight. Some do no gain weight well because they have difficulty sucking and swallowing, while others may not grow well even though they are eating well.
Some older children with 1p36 Deletion Syndrome become overweight. Dietary changes, special feeding techniques or other medical interventions may be needed to manage the growth problems associated with this condition.
- Characteristic physical features: Young children with 1p36 Deletion Syndrome tend to look similar.
They often have a small head, a large fontanel (soft spot), deep-set eyes, short eye openings, a flat nose with a broad nasal tip, a prominent forehead, low set ears, ear asymmetry, a small mouth and a small pointed chin.
- Developmental delay: Most young children with 1p36 Deletion Syndrome sit up, walk and talk later than usual.
Speech is often more delayed than other skills. Many individuals with 1p36 Deletion Syndrome have difficulty talking and may benefit from the use of sign language or assisted communication devices.
Early intervention services and intensive speech therapy are recommended to maximize an individual’s abilities.
- Intellectual disability: Older children and adults with 1p36 Deletion Syndrome have some degree of intellectual disability.
Some children with 1p36 Deletion Syndrome can talk and assist in their daily care, while others are not verbal and require constant care.
Although the degree of intellectual disability may be somewhat dependent on the size of the deletion, there is presently no way to accurately predict what an infant’s IQ will be when they grow up.
- Congenital malformations: Babies with 1p36 Deletion Syndrome may be born with birth defects such as cleft lip, cleft palate, structural heart defects or malformations of the brain. Surgery may help correct some of these problems.
- Cardiomyopathy: Some infants with 1p36 Deletion Syndrome have infantile dilated cardiomyopathy. With cardiomyopathy, the heart is enlarged and doesn’t pump as strongly as it should. When necessary, medication sometimes helps improve cardiac function.
- Hearing loss:Conductive or sensorineural hearing loss occurs quite frequently in children with 1p36 Deletion Syndrome. Treatment for hearing loss is usually the same as it is for children with other causes of hearing loss.
- Vision or eye problems: A number of different types of vision and eye problems have been reported in children with 1p36 Deletion Syndrome.
Vision problems can usually be improved with glasses or other interventions.
- Thyroid problems: Children with 1p36 Deletion Syndrome seem to be at an increased risk of developing thyroid problems, the most common being hypothyroidism.
Hypothyroidism occurs when the thyroid gland does not make enough of a hormone that is necessary for growth and development. When diagnosed, hypothyroidism can be treated successfully with medication.
- Behavior problems: A number of behavior problems have been reported in children with 1p36 Deletion Syndrome.
These include self-injuring behavior, banging or throwing objects, hitting people and screaming episodes. Child psychiatrists or psychologists can recommend strategies and medications that may help with behavior problems if they arise.
- Rare complications: Additional, less common findings reported in children with 1p36 Deletion Syndrome include early onset of puberty (precocious puberty), abnormal curvature of the spine (scoliosis), minor vertebral abnormalities, and testes that have not descended into the scrotum at birth (cryptochirdism).
Other uncommon medical complications may include neuroblastoma (a type of abdominal tumor that occurs almost exclusively in early childhood).
Neuroblastoma is rare and has only been reported in a few children with 1p36 Deletion Syndrome or a chromosome rearrangement involving 1p36.
What is the treatment for 1p36 deletion syndrome?
Treatment is limited; symptomatic treatment is the usual treatment available. The heart, eye, muscle tone, and swallowing problems may be reduced by specialists in those fields; the earlier the diagnosis and treatment, the more likely these problems will become manageable or minimized.
Some clinicians report good results with behavior modification training. Some affected individuals do well and can participate in many social events, but not all individuals are successful.
Compassion, patience and understanding of the extent of an individual’s capabilities can allow an individual to have a loving and rewarding relationship with family and friends.
Some affected individuals may be able to learn to communicate with body and sign language; this ability may take considerable effort and training on both the affected person and caregiver’s part to develop.
What is the prognosis and life expectancy for 1p36 deletion syndrome?
Part of the prognosis for individuals with 1p36 deletion syndrome really depends on how much of DNA is missing from the p36 region.
Some researchers now list p36 as p36.1 to p36.3, with p36.3 as the most amount of DNA missing and having the worst prognosis (poor, with severe symptoms).
However, even these individuals may have some responses to the treatment listed above. Consequently, some individuals may have a relative good prognosis (a loving relationship with understanding and patient caregivers and family members) to a poor prognosis and early death from significant physical problems.
1p36 deletion syndrome is so new that data on projected lifespan is lacking. However, there are reports in the medical literature that some patients reach adulthood.
How many of those that have the syndrome now and live on will help determine the life expectancy for future patients with 1p36 deficiency syndrome.
Current research is focusing on collecting blood from families with a child who has been diagnosed with a chromosomal disorder including microdeletions in order to further develop a non-invasive prenatal screening test based on fetal DNA isolated from maternal blood.