What is Jacobsen syndrome?
Jacobsen syndrome is a rare congenital condition that’s caused by the deletion of several genes in chromosome 11. It’s sometimes called partial monosomy 11q. It occurs in about 1 in 100,000 newborns.
Jacobsen syndrome often causes:
- birth defects
- behavioral problems
- impairment of memory and thinking skills
Jacobsen syndrome is also associated with autism. It can result in a number of serious health complications.
What are the symptoms of Jacobsen syndrome?
Jacobsen syndrome causes a wide range of symptoms and physical defects.
One of the initial symptoms parents may notice is abnormally slow growth, both in the womb and after birth. Many people with Jacobsen syndrome will be shorter than average at their adult height. They may also have macrocephaly, or a larger-than-average head size. Trigonocephaly is another common symptom. This gives the forehead a pointed look.
Other physical symptoms include distinctive facial features. These include:
- wide-set eyes with droopy eyelids
- small and low-set ears
- a broad nasal bridge
- downturned corners of the mouth
- a small lower jaw
- a thin upper lip
- skin folds covering the inner corners of the eyes
Many people with Jacobsen syndrome will have cognitive impairment. This can translate to delayed development, including the development of both speech and motor skills. Some infants will have difficulty feeding. Many will also have learning disabilities, which may be severe.
Behavioral problems are also symptoms associated with Jacobsen syndrome. These can be related to compulsive behavior, easy distractibility, and a short attention span. Many patients have both Jacobsen syndrome and ADHD. It’s also associated with autism.
What causes Jacobsen syndrome?
Jacobsen syndrome is caused by a loss of genetic material in chromosome 11. This occurs as an entirely random error in cell division in most cases. This normally occurs during the formation of reproductive cells or early on during fetal development. The number of genes deleted from the chromosome will determine how severe the disorder is.
Most cases of Jacobsen syndrome are not inherited. Only between 5 and 10 percent of cases occur when a child inherits the disorder from an unaffected parent. These parents have genetic material that is rearranged but still present in chromosome 11. This is called balanced translocation. If Jacobsen syndrome is inherited, parents have a slightly higher risk of having another child with the condition.
Girls are twice as likely to develop this syndrome than boys.
How is Jacobsen syndrome diagnosed?
Diagnosing Jacobsen syndrome can be difficult in some cases. This is because it is both a genetic condition and a rare one. Genetic testing is necessary to confirm a Jacobsen syndrome diagnosis.
During genetic testing, magnified chromosomes are evaluated under a microscope. They’re stained to give them a “barcode” appearance. The broken chromosome and the genes that have been deleted will be visible.
Jacobsen syndrome can be diagnosed during pregnancy. If an ultrasound flags anything abnormal, further testing may be done. A blood sample can be taken from the mother and analyzed.
Can Jacbosen syndrome cause complications?
Jacobsen syndrome can result in a large number of serious complications.
Learning disabilities affect about 97 percent of individuals with Jacobsen syndrome. These learning difficulties are typically mild to moderate. They can be severe.
Bleeding disorders are a serious but common complication of Jacobsen syndrome. About 88 percent of children with Jacobsen syndrome are born with Paris-Trousseau syndrome. This is a bleeding disorder that makes you bruise easily or bleed a lot. This can put you at a risk for internal bleeding. Even nosebleeds or blood work can result in heavy blood loss.
Heart conditions are also a common complication. About 56 percent of children with Jacobsen syndrome are born with heart conditions. Some of these will need surgery to be treated. About 20 percent of children with Jacobsen will die of heart complications before they’re 2 years old. Common heart defects include:
- holes between the left and right lower chambers
- abnormalities on the left side of the heart
- hypoplastic left heart syndrome, a defect that affects blood flow through the heart
Kidney problems can occur in infants and children with Jacobsen. Kidney problems include:
- having a single kidney
- double ureters (the tubes leading from the kidneys to the bladder)
- hydroneprosis, or swelling
Gastrointestinal problems commonly affect infants with this condition. Pyloric stenosis causes forceful vomiting because of a narrowed or blocked outlet from the stomachs to the intestines. Other common problems include:
- blocked or narrow anus
- intestinal obstruction
- missing parts of the GI tract
- abnormal positioning of the gut
Many children with Jacobsen have eye disorders that affect their sight, but a lot of these complications can be treated. Some children will develop cataracts.
Because some children with Jacobsen syndrome are immunodeficient, they may be much more susceptible to infections. Ear and sinus infections are especially common. Some children will have such severe ear infections they may get hearing loss.
Coping with Jacobsen syndrome
Having a child with Jacobsen syndrome can be difficult for parents, especially since the disorder is so rare. Finding support can help you cope and give you the tools you need to help your child. Your child’s pediatrician may have suggestions for where you can find support.
Other great resources for parents of children with Jacobsen syndrome include:
- 11q Research & Resource Group
- Chromosome Disorder Outreach
- Unique- Rare Chromosome Disorder Support Group
What is the Outlook for Jacobsen Syndrome?
There is no cure for Jacobsen syndrome, so treatment will focus on improving the child’s overall health. Treatment will focus on addressing health complications that arise and helping the child reach developmental milestones.
The life expectancy of children with this condition is unknown, but individuals can and have lived into adulthood. Many adults with Jacobsen syndrome can live happy, fulfilling, and semi-independent lives.