Information sheet about Jacobsen syndrome

Other Names

11q deletion syndrome; 11q deletion disorder; 11q terminal deletion disorder; partial 11q monosomy syndrome; 11q23 deletion disorder; Jacobsen thrombocytopenia; del(11)(q23.3); del(11)(qter); distal deletion 11q; distal monosomy 11q; monosomy 11qter; telomeric deletion 11q; JBS.


Blood diseases; chromosome disorders; congenital and genetic diseases; rare diseases; eye diseases

Signs and Symptoms

The signs and symptoms of Jacobsen syndrome vary among people but often include:

  • cognitive impairment which can translate to delayed development, including the development of both speech and motor skills and learning difficulties
  • a bleeding disorder called Paris-Trousseau syndrome in which blood clots poorly, causes easy bruising and bleeding and increases the risk of internal bleeding
  • distinctive facial features; the most often reported features include, small and low-set ears, widely set eyes (hypertelorism) with droopy eyelids (ptosis), skin folds covering the inner corner of the eyes (epicanthic folds), a broad nasal bridge, downturned corners of the mouth, a thin upper lip, and a small lower jaw, a large head size (macrocephaly) and a skull abnormality called trigonocephaly, which gives the forehead a pointed appearance
  • behavioural issues, e.g compulsive behaviour
  • attention deficit-hyperactivity disorder (ADHD) and the possibility of autism spectrum disorders
  • other features can include congenital heart defects, feeding difficulties in infancy, short stature, frequent ear and sinus infections, skeletal abnormalities, problems with vision (eye disorders), hormones and the immune system (immunodeficient)
  • the disorder can also affect the digestive system (e.g. pyloric stenosis, obstructions), kidneys (e.g. single kidney, double ureters, cysts), and genitalia (e.g. undescended testes)
  • about 20% of children die during the first two years of life, most commonly due to complications from congenital heart disease, and less commonly from bleeding
  • 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
  • 85% of cases are not inherited. They occur as a random event during the formation of reproductive cells (eggs or sperm) or in early foetal development
  • in the other 15% of cases, an affected person inherits the deletion from one unaffected parent who has a balanced translocation (when a piece of one chromosome breaks off and attaches to another chromosome)
  • the size of the deletion varies among affected individuals, larger deletions tend to cause more severe signs and symptoms than smaller deletions
  • the specific features of Jacobsen syndrome relate to the loss of multiple genes within the deleted region. While the exact function of some of the genes involved is unclear, they appear to be critical for the usual expected development of many parts of the body.
  • only a few of these genes have been studied as possible contributors to the specific features of Jacobsen syndrome; researchers are working to determine which additional genes may be associated with this condition
  • girls are twice as likely to develop this syndrome as boys
  • differential diagnoses include Turner and Noonan syndromes, and acquired thrombocytopenia due to sepsis
  • prenatal diagnosis of 11q deletion is possible by amniocentesis or chorionic villus sampling and cytogenetic analysis.

Treatment and Management

There is no cure for Jacobsen syndrome; treatment focuses on the specific signs and symptoms for each individual. Treatment may require the coordinated efforts of a team of specialists.

For example:

  • individuals with low platelet counts (thrombocytopenia) should be monitored regularly. Blood or platelet transfusions may be necessary before or during surgeries.
  • cardiac malformations can be very severe and require heart surgery in the neonatal period.
  • complications of certain congenital heart defects (such as rapid heartbeat or fluid accumulation) may be treated with drugs.
  • respiratory infections should be treated as soon as possible because of the risk of bacterial infection of the heart lining (endocarditis) and valves, antibiotics may be needed before any surgery depending on the cardiac issues an individual is managing.
  • eye abnormalities may be treated with surgery, glasses, contact lenses, and/or other measures to improve vision.
  • abnormalities of the joints, tendons, muscles, and bones may be treated with surgery or other measures and physiotherapy may help improve coordination and mobility. Early intervention is important to ensure that children reach their full potential.

Support Contacts Australia

Australian Rare Chromosome Awareness Network (ARCAN) http://www.arcan.org.au/

Facebook Support

Jacobsen syndrome https://www.facebook.com/groups/jacobsensyndrome/

The 11q Research and Resource Group Updates, Events and Fundraising


European Chromosome 11 Network


Support Contacts International

Unique https://www.rarechromo.org

11q deletion disorder: Jacobsen syndrome guide


European Chromosome 11 Network www.chromosome11.eu

11q Research and Resource Group www.11qusa.org

Chromosome Disorder Outreach https://chromodisorder.org/


Genetics Home Reference https://ghr.nlm.nih.gov/condition/jacobsen-syndrome

National Center for Biotechnology Information https://www.ncbi.nlm.nih.gov/pubmed/19267933

Genetic and Rare Diseases Information Center https://rarediseases.info.nih.gov/diseases/307/jacobsen-syndrome

Orphanet https://www.orpha.net/consor/cgi-bin/Disease_Search.php?lng=EN&data_id=518&Disease_Disease_Search_diseaseGroup=Jacobsen-syndrome&Disease_Disease_Search_diseaseType=Pat&Disease(s)/group%20of%20diseases=Jacobsen-syndrome&title=Jacobsen%20syndrome&search=Disease_Search_Simple

Healthline https://www.healthline.com/health/jacobsen-syndrome


Disclaimer: This information is for general use only and is not meant to be a substitute for seeking professional care in the diagnosis, treatment and management of this condition.

Last update Sept 2018