A rare disorder that is a type of chromosomal disorder and causes a deletion of a few genes at the end of the long arm of chromosome 11 is called Jacobsen syndrome. It also causes specific facial features and symptoms (such as developmental delays and heart defects).
In some cases, this condition is called 11q terminal deletion disorder, and some people lose only a small part of the 11q chromosome. It means they have smaller deletions and milder symptoms compared to those who have larger deletions. It is also known as partial Jacobsen syndrome, which means only a part of one chromosome in a pair is deleted.
Those who develop this syndrome also experience developmental delays, behavioral problems, and distinctive facial features. Furthermore, there is an increased risk of people with congenital heart defects along with Jacobsen syndrome. Unfortunately, there is no way to cure this syndrome. That’s why the treatment goal is to manage the symptoms and prevent serious complications until the affected person reaches developmental milestones.
What Are The Symptoms of Jacobsen Syndrome?
The symptoms may appear differently among people who develop this syndrome. It often depends on the size and location of the chromosomal deletion. However, most of them experience delays in their speech and motor skills. Others may also experience learning disabilities and cognitive impairment. Moreover, many children with this syndrome also have attention-deficit/hyperactivity disorder (ADHD), which is a risk factor for autism spectrum disorder. Check below for other facial characteristics of people with Jacobsen syndrome:
- Macrocephaly (large head)
- Trigonocephaly (a pointed forehead, which is caused by a skull abnormality)
- Low-set and small ears
- Ptosis (drooping eyelids)
- Hypertelorism (widely set eyes)
- Wide nose bridge
- Epicanthal folds (these are certain skin pieces that cover the inner corner of the eyes)
- Downturned corners of the mouth
- Small lower jaw and thin upper lip
If your child has any of the previous symptoms, immediately contact your healthcare professional. Otherwise, it may lead to unpleasant outcomes.
Causes
In normal circumstances, chromosomes are a part of the body that contain genes (genetic material). These genes are responsible for the proper development and function of the body (including the heart, brain, and facial features). Healthy people have 22 numbered pairs of chromosomes and one pair of sex chromosomes. Each one has a short (p) arm and a long (q) arm. In people with Jacobsen syndrome, there is a deletion of genes on the long (q) arm of chromosome 11. Usually, the rest of this chromosome is intact. The symptoms of this condition vary from mild to severe because they depend on how many genes are deleted from this chromosome.
Is Jacobsen Syndrome Recessive or Dominant?
These medical terms are used to describe the way you receive the abnormal genes from each biological parent. Most of the time, this condition is not inherited and occurs from a chromosomal deletion that happens randomly. It often happens during fetal development, and there is nothing that parents can do to cause this deletion. Most people with this syndrome do not have a family history of the disease. Unfortunately, they can pass the abnormal gene to their children in the future.
Sometimes, this condition happens when a person inherits the deletion from an unaffected parent. In this case, the parent carries the chromosomal rearrangement (a balanced translocation). Furthermore, some recent studies have found that Jacobsen syndrome mostly affects girls.
What Are The Possible Complications of Jacobsen Syndrome?
People with this syndrome may also experience some complications, especially if the condition is poorly managed. However, there are some complications that are present at birth (congenital). Check some examples below:
- Short stature
- Growth delay before and after birth
- Frequent ear and sinus infections
- Abnormalities of the digestive system, genitalia, and kidneys
- Congenital heart defects
- Feeling problems
- Paris-Trousseau syndrome – This is a blood disorder that causes reduced platelet count and abnormal function of these blood cells. Typically, platelets are responsible for blood clotting, and people with this complication may experience severe internal or external bleeding.
- Heart failure
This article does not contain a full list of Jacobsen syndrome complications. However, doctors may recommend some options to reduce the risk of developing them. Additionally, there is no way to prevent this condition. The only thing you can do is take a genetic test to make sure you do not have the abnormal gene that can be passed to your child. It is very important to understand the risks of having children with this syndrome.
Diagnosis
Typically, it is difficult to diagnose this condition, especially during pregnancy. When a prenatal ultrasound scan indicates concerns, doctors may perform additional tests. Some of them are listed below:
- NIPT (non-invasive prenatal testing) – During this test, physicians will look for abnormal chromosome numbers in small amounts of fetal DNA that is found in the blood.
- CVS (chorionic villus sampling) – This test involves a needle that helps take a sample of cells from the placenta for testing.
- Amniocentesis – It also involves a needle to get a sample of amniotic fluid for testing.
After birth, physicians may perform a genetic test. During this test, they will take a blood sample to check for abnormal genes that cause Jacobsen syndrome. However, in some cases, this is not enough to confirm or rule out this syndrome. That’s why doctors may also perform an additional test called microarray comparative genomic hybridization (array CGH). It can identify duplicated, disrupted, or even missing DNA.
Treatment
This syndrome cannot be cured. Thus, doctors will recommend treatments to ease the symptoms and prevent complications. Check some common options below:
- Surgery – These include a fundoplication (to correct the problems with the valve at the bottom of the esophagus) and other surgeries to repair skull and face abnormalities, vision problems, skeletal or cardiac defects, and others.
- Diuretics (also known as water pills) – These medicines are used to remove excess fluid from the body.
- Antiarrhythmics – This group of medications is used to prevent or treat irregular heart rhythm.
- Blood thinners (also called anticoagulants) – Doctors often recommend Desmopressin to prevent or treat blood clots.
- Physical and speech therapy
- Special remedial education
Frequently Asked Questions
Is Jacobsen syndrome a genetic disorder?
Yes, Jacobsen syndrome is a genetic disorder caused by the deletion of genetic material from the end of the long arm (q arm) of chromosome 11. Although it involves genes, most cases are not inherited from a parent and occur as a random chromosomal change.
What causes Jacobsen syndrome?
Jacobsen syndrome occurs when a portion of chromosome 11q is missing. The deletion can occur spontaneously during the formation of reproductive cells or early fetal development. In some cases, it can result from an inherited unbalanced chromosome rearrangement involving a parent.
Can Jacobsen syndrome be inherited?
Most cases of Jacobsen syndrome are not inherited. However, a person with the condition may be able to pass the chromosome deletion or a related chromosome rearrangement to their children. In rare cases, an unaffected parent who carries a balanced translocation can have a child with Jacobsen syndrome.
Does Jacobsen syndrome affect life expectancy?
Life expectancy varies considerably depending on the size of the chromosome deletion and the health problems it causes. Severe congenital heart defects, bleeding problems, and other serious complications can affect survival, while some people with milder forms may live into adulthood.
Can Jacobsen syndrome be diagnosed before birth?
Jacobsen syndrome may sometimes be suspected during pregnancy when an ultrasound shows certain abnormalities, such as growth restriction or structural heart problems. Prenatal testing, including chorionic villus sampling (CVS) or amniocentesis, can be used to analyze fetal chromosomes. Screening tests such as NIPT may also identify an increased risk, but diagnostic testing is needed for confirmation.
What tests are used to diagnose Jacobsen syndrome after birth?
Doctors may use chromosome analysis and chromosomal microarray testing to identify missing genetic material on chromosome 11. A chromosomal microarray can determine whether a section of chromosome 11 is deleted and can provide information about the size of the deletion. Additional genetic testing may be recommended in some cases.
What health problems are associated with Jacobsen syndrome?
Jacobsen syndrome can affect several parts of the body. Common problems include developmental and learning difficulties, speech and motor delays, congenital heart defects, growth problems, hearing or vision abnormalities, and bleeding problems related to low or abnormal platelets. Kidney, gastrointestinal, skeletal, and immune-system problems may also occur.
Does Jacobsen syndrome affect development and learning?
Many children with Jacobsen syndrome have developmental delays, particularly involving speech, motor skills, and learning. The severity varies between individuals. Early intervention, speech therapy, physical therapy, occupational therapy, and appropriate educational support can help children develop their abilities.
Is there a cure for Jacobsen syndrome?
There is currently no cure that can replace the missing chromosome material. Treatment focuses on managing individual symptoms and complications. Depending on the person’s needs, care may involve cardiology, developmental services, speech and physical therapy, surgery, educational support, and regular monitoring for associated health problems.
Can parents prevent Jacobsen syndrome?
In most cases, there is nothing parents can do to prevent Jacobsen syndrome because the chromosome deletion occurs randomly. If a child has Jacobsen syndrome, genetic counseling can help determine whether a parent carries a chromosome rearrangement and can explain the potential risk in future pregnancies. If you have any other questions, ask your doctor.
