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Jacobsen syndrome
Also known as 11q23-q25 deletion · 11q terminal deletion · Paris-Trousseau syndrome
This condition can affect many parts of the body, leading to developmental delay, distinctive facial features, heart problems, and a bleeding disorder. It is present from birth and affects approximately 1 in 100,000 live births.
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Overview
Jacobsen syndrome, also known as 11q terminal deletion disorder, is a rare genetic condition resulting from a missing piece of genetic material at the end of the long arm (q arm) of chromosome 11 [PMID:33261642]. This deletion typically starts at band 11q23 and can extend to the end of the chromosome, 11qter. The size of the deleted segment varies among affected individuals, influencing the range and severity of symptoms experienced.
This condition can lead to a wide spectrum of health and developmental challenges, which may include intellectual disability, distinctive facial features, heart abnormalities, and a blood clotting disorder called Paris-Trousseau syndrome. While present from birth, the specific combination and severity of features can differ greatly between individuals with Jacobsen syndrome.
Symptoms & clinical features
Individuals with Jacobsen syndrome often present with a characteristic set of features. Developmental delay is common, affecting abilities such as sitting, walking, and speaking, and ranging from mild to severe [PMID:33261642]. Intellectual disability is also frequently observed.
Physical characteristics can include distinctive facial features, such as a large head (macrocephaly), widely spaced eyes (hypertelorism), downward-sloping eyelids, skin folds covering the inner corner of the eyes (epicanthal folds), a broad nasal bridge, V-shaped mouth, and small, low-set ears. Many-finger-and-toe abnormalities, such as short fingers (brachydactyly) or fifth fingers that curve inwards (clinodactyly), may also be present. Heart defects are found in approximately 50-70% of individuals with Jacobsen syndrome, ranging from mild to severe [PMID:33261642].
A notable symptom associated with Jacobsen syndrome is Paris-Trousseau syndrome, a bleeding disorder caused by problems with blood platelets. This condition can lead to easy bruising and prolonged bleeding due to a reduction in the number of platelets and their impaired function [PMID:24075114]. Other potential health issues can include feeding difficulties in infancy, kidney problems, gastrointestinal issues, immune system dysfunction, and skeletal abnormalities.
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Affected organs
Jacobsen syndrome can impact numerous organ systems throughout the body. The brain is often affected, leading to developmental delay and intellectual disability. The heart is frequently involved, with many individuals experiencing congenital heart defects. Blood-forming tissues are also affected, resulting in Paris-Trousseau syndrome, which impacts platelet formation and function.
The skeletal system can be affected, leading to bone and limb abnormalities. Other systems that may be involved include the kidneys, gastrointestinal tract, and the immune system, all contributing to the varied presentation of the condition.
Risks & severity
The severity of Jacobsen syndrome can vary significantly, even among individuals with similar-sized deletions. The specific genes located within the deleted segment contribute to the range of symptoms [PMID:33261642]. Larger deletions generally correlate with more severe symptoms and developmental challenges. Life-threatening complications, particularly those related to severe heart defects or chronic bleeding from Paris-Trousseau syndrome, can occur.
Unfortunately, approximately 20% of children with Jacobsen syndrome do not survive beyond two years of age, often due to congenital heart defects or complications from the bleeding disorder [PMID:33261642]. However, with careful medical management and ongoing support, many individuals can live into adulthood. The long-term outlook depends heavily on the specific health issues present and the quality of supportive care received.
Genetic causes
Jacobsen syndrome is a chromosomal disorder caused by a deletion (a missing segment) on the long arm of chromosome 11. This deletion typically encompasses several genes, and the loss of these genes is responsible for the diverse range of symptoms seen in affected individuals. The critical region for Jacobsen syndrome is generally considered to be 11q23-q25, with the size of the deletion influencing the clinical features.
Two specific genes often implicated in the features of Jacobsen syndrome are *ETS1* and *FLI1*. The *ETS1* gene plays a role in various cellular processes, including cell development and growth, and its loss may contribute to certain developmental and neurological issues. The *FLI1* gene is vital for the proper development and function of blood cells, particularly platelets, and its absence or disruption is directly linked to the bleeding condition observed in Paris-Trousseau syndrome [PMID:24075114]. The collective loss of these and other genes within the deleted region leads to the complex set of signs and symptoms characteristic of Jacobsen syndrome.
- ETS1 ETS proto-oncogene 1, transcription factor
- FLI1 Fli-1 proto-oncogene, ETS transcription factor
Inheritance pattern
Jacobsen syndrome is typically a sporadic condition, meaning it occurs randomly and is not inherited from either parent. In about 85-90% of cases, the deletion on chromosome 11 happens during the formation of reproductive cells (eggs or sperm) or during early foetal development. In such instances, neither parent carries the deletion.
In a smaller number of cases, approximately 5-15%, an affected individual may inherit the deletion from a parent who carries a balanced chromosomal rearrangement, such as a translocation. A balanced translocation means that parts of chromosomes have swapped places, but no genetic material has been gained or lost, so the parent is usually healthy. However, when this parent passes on their chromosomes, there is a chance that the child will inherit an unbalanced set, resulting in a deletion like that seen in Jacobsen syndrome. For families with a parent carrying a balanced rearrangement, genetic counselling can provide detailed information about recurrence risks for future children.
Diagnosis & testing
Diagnosis of Jacobsen syndrome is usually suspected based on characteristic clinical features observed at birth or early in life. Confirmation of the diagnosis requires genetic testing to identify the specific chromosomal deletion. Karyotyping, which examines the structure of chromosomes, can sometimes detect larger deletions. However, more detailed techniques are often needed.
Chromosomal microarray analysis (CMA) is a highly sensitive test that can detect small missing or extra pieces of genetic material across all chromosomes, making it a common method for confirming Jacobsen syndrome. Fluorescent in situ hybridisation (FISH) can also be used to specifically look for deletions in the 11q23 region. In the UK, genetic testing for suspected chromosomal anomalies, including Jacobsen syndrome, typically falls under the NHS Genomic Medicine Service (GMS) pathways. Referrals for such testing are usually made by paediatricians, clinical geneticists, or other specialist clinicians when Jacobsen syndrome is suspected. The relevant R-codes for genomic testing would be determined by the specific GMS testing directory.
Management & lifestyle
Due to the wide range of potential health challenges, management of Jacobsen syndrome requires a multidisciplinary approach, with care coordinated by a team of specialists. This team may include paediatricians, cardiologists for heart defects, haematologists for Paris-Trousseau syndrome, developmental paediatricians, neurologists, and therapists (e.g., physiotherapists, occupational therapists, speech and language therapists).
Regular monitoring is crucial, especially for cardiac function and bleeding tendencies. Specific treatments are directed at managing individual symptoms; for example, surgery for complex heart defects, or interventions for developmental delays. Early intervention programmes, including therapies and educational support, are highly beneficial for optimising developmental outcomes. Genetic counselling is an important part of care, providing families with information about the condition, inheritance patterns, and support services. Management plans are always individualised, focusing on the specific needs of each affected person.
UK care pathway
In the UK, individuals suspected of having Jacobsen syndrome are typically referred to clinical genetics services within the NHS. This ensures access to specialist genetic testing, often through the NHS Genomic Medicine Service (GMS), which uses national R-codes to guide appropriate genomic investigations. Following diagnosis, care is usually coordinated by a paediatrician, alongside input from various specialist teams depending on the symptoms present. Genetic counsellors play a key role in providing information, emotional support, and discussing implications for families.
Frequently asked questions
Is Jacobsen syndrome always inherited?
No, Jacobsen syndrome is usually not inherited. In most cases, the deletion happens randomly during the formation of reproductive cells or early foetal development. Only in a small percentage of cases is it inherited from a parent who carries a balanced chromosomal change.
What is Paris-Trousseau syndrome?
Paris-Trousseau syndrome is a bleeding disorder specifically associated with Jacobsen syndrome. It is caused by problems with blood platelets, which are essential for clotting. This can lead to easier bruising and prolonged bleeding.
How common is Jacobsen syndrome?
Jacobsen syndrome is a rare condition, affecting approximately 1 in 100,000 live births. Its rarity means that many healthcare professionals may have limited experience with it.
Can the severity of Jacobsen syndrome vary?
Yes, the severity of Jacobsen syndrome can vary significantly between individuals. This is mainly because the size of the deleted segment on chromosome 11 can differ, and a larger deletion often leads to more pronounced symptoms. The specific genes lost also influence the clinical picture.
What should I do if I suspect my child has Jacobsen syndrome?
If you suspect your child has Jacobsen syndrome or shows symptoms consistent with it, you should discuss your concerns with your GP or paediatrician. They can arrange for appropriate specialist referrals, such as to a clinical geneticist, for further evaluation and genetic testing.
References
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- OBrien MP, Corado A. Jacobsen Syndrome (11q Terminal Deletion Syndrome). 2025. PMID: 40334032
- Clang DR, LaBaere Ii RJ. Jacobsen syndrome: Chromosome deletion at llq23. Journal of osteopathic medicine. 1998. PMID: 39479911
- Lukusa T, Fryns JP. Human chromosome fragility. Biochimica et biophysica acta. 2008. PMID: 18078840
- Tubbs AS, Combs D, Grandner MA. Obstructive Sleep Apnea in Jacobsen Syndrome. Sleep and vigilance. 2019. PMID: 34296059
- Urschel D, Hernandez-Trujillo VP. Spectrum of Genetic T-Cell Disorders from 22q11.2DS to CHARGE. Clinical reviews in allergy & immunology. 2022. PMID: 35133619