Other Names for this Disease
- Chromosome 11q deletion syndrome
- Partial 11q monosomy syndrome
What are the signs and symptoms of Jacobsen syndrome?
What causes Jacobsen syndrome?
How might Jacobsen syndrome be treated?
The signs and symptoms of Jacobsen syndrome vary among people with this condition. Most affected individuals have delayed development, including the development of motor skills (such as sitting, standing, and walking) and speech. Most also have cognitive impairment and learning difficulties. Behavioral problems have been reported, including compulsive behavior (such as shredding paper), a short attention span, and being easily distractd. Many people with Jacobsen syndrome have been diagnosed with attention deficit-hyperactivity disorder (ADHD).
Jacobsen syndrome is also characterized by distinctive facial features. These include small and low-set ears, widely set eyes (hypertelorism) with droopy eyelids (ptosis), skin folds covering the inner corner of the eyes (epicanthal folds), a broad nasal bridge, downturned corners of the mouth, a thin upper lip, and a small lower jaw. Affected individuals often have a large head size (macrocephaly) and a skull abnormality called trigonocephaly, which gives the forehead a pointed appearance.
More than 90 percent of people with Jacobsen syndrome have a bleeding disorder called Paris-Trousseau syndrome. This condition causes a lifelong risk of abnormal bleeding and easy bruising. Paris-Trousseau syndrome is a disorder of platelets, which are blood cell fragments that are necessary for blood clotting.
Other features of Jacobsen syndrome can include heart defects, feeding difficulties in infancy, short stature, frequent ear and sinus infections, and skeletal abnormalities. The disorder can also affect the digestive system, kidneys, and genitalia. The life expectancy of people with Jacobsen syndrome is unknown, although affected individuals have lived into adulthood.
Jacobsen syndrome is caused by a deletion of genetic material at the end of the long (q) arm of chromosome 11. The size of the deletion varies among affected individuals, with most affected people missing from about 5 million to 16 million DNA building blocks (also written as 5 Mb to 16 Mb). In almost all affected people, the deletion includes the tip of chromosome 11. Larger deletions tend to cause more severe signs and symptoms than smaller deletions.
The features of Jacobsen syndrome are likely related to the loss of multiple genes on chromosome 11. Depending on its size, the deleted region can contain from about 170 to more than 340 genes. Many of these genes have not been well characterized. However, genes in this region appear to be critical for the normal development of many parts of the body, including the brain, facial features, and heart. Researchers are working to determine which genes contribute to the specific features of Jacobsen syndrome.
Individuals with low platelet counts (thrombocytopenia) should be monitored regularly. Blood or platelet transfusions may be necessary before or during surgeries. Surgery may be needed to repair various malformations associated with the condition. Complications of certain congenital heart defects (such as rapid heartbeat or fluid accumulation) may be treated with a variety of drugs. Respiratory infections should be treated vigorously and early. Because of the risk of bacterial infection of the heart lining (endocarditis) and valves, those with certain heart defects may need antibiotics before any surgery.
Eye abnormalities may be treated with surgery, glasses, contact lenses, and/or other measures to improve visual problems. Abnormalities of the joints, tendons, muscles, and bones may be treated by orthopedic techniques, potentially in combination with surgery. Physical therapy may help improve coordination and mobility. Early intervention is important to ensure that affected children reach their full potential.
- Jacobsen syndrome. Genetics Home Reference (GHR). 2009; http://ghr.nlm.nih.gov/condition/jacobsen-syndrome. Accessed 9/20/2010.
- Chromosome 11, Partial Monosomy 11q. NORD. April 26, 2012; http://rarediseases.org/rare-disease-information/rare-diseases/byID/641/viewAbstract. Accessed 5/30/2012.