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Jacobsen Syndrome

Last updated July 20, 2016

NIH

Image showing Facial dysmophism in Jacobsen syndrome patients.


What are the other Names for this Condition? (Also known as/Symptoms)

  • 11q Terminal Deletion Disorder
  • Chromosome 11q Deletion Syndrome
  • Del(11)(q23.3)

What is Jacobsen Syndrome? (Definition/Background Information)

  • Jacobsen Syndrome, also known as Chromosome 11q Deletion Syndrome, is a rare chromosomal disorder. In this syndrome, there is a loss of genetic material in the long arm of chromosome 11
  • Approximately (and only) 5-10% of individuals with Jacobsen Syndrome (JBS) have a family history of the condition. Since nearly two-thirds of the reported cases are in females, belonging to the female gender may be considered a risk factor for JBS
  • The types and severity of symptoms depends upon the amount of genetic material lost. Severity of Jacobsen Syndrome also depends on whether an individual has a mixture of normal and abnormal cells (mosaicism), or if all of their cells are abnormal
  • The main signs and symptoms of Jacobsen Syndrome are distinctive facial features (small ears, widely-spaced eyes, droopy eyelids), developmental delays (affecting speech, motor skills, coordination), problems with cognition (learning disability), behavioral issues (attention deficiency), and abnormal bleeding owing to abnormal platelets
  • A healthcare professional typically uses physical examination, assessment of symptoms, and genetic testing, in order to diagnose and confirm Jacobsen Syndrome
  • Many complications can arise in individuals with Jacobsen Syndrome including heart disease, frequent infections, skeletal abnormalities, gastrointestinal (GI) tract problems, kidney malfunction, and forceful vomiting
  • The management of Jacobsen Syndrome typically requires a team of qualified specialists from various disciplines including speech therapy, behavioral therapy, cardiology, neurology, and ophthalmology, along with the active support of family members
  • Jacobsen Syndrome is fatal in about 1 in 5 cases; the deaths are reported within the first 2 years of life. There are reports of some individuals reaching adulthood; however, a majority of individuals have significantly shortened life spans

Who gets Jacobsen Syndrome? (Age and Sex Distribution)

  • Jacobsen Syndrome is a rare chromosomal disorder that is estimated to affect 1 in every 100,000 newborns. Over 200 cases have so far been reported in the medical literature
  • Although the disorder can potentially affect both genders, females are twice as likely to be affected than males (female-male ratio is 2:1)
  • No particular preference for any race or ethnicity is reported

What are the Risk Factors for Jacobsen Syndrome? (Predisposing Factors)

The specific risk factors for Jacobsen Syndrome are currently not well understood, since the condition occurs due to a spontaneous deletion during cell division. Nevertheless, the following may be noted:

  • In about 5-10% of the individuals with inherited form of the syndrome, family history may be a risk factor
  • Since nearly 65% of the affected individuals are reported to be females, the female gender may be termed as a risk factor for developing Jacobsen Syndrome

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Jacobsen Syndrome? (Etiology)

Jacobsen Syndrome is a very well-studied genetic disorder, which is caused by the deletion of a part of chromosome 11.

  • Loss of genetic material from chromosome 11 due to a spontaneous deletion
    • This occurs during the formation of gametes (egg and sperm) or in the early fetal developmental stages
    • The deletion frequently occurs in the end or terminal region of the chromosome, and the loss of genetic material could vary from 5-16 million genetic building blocks
    • The size of deletion could result in the loss of 170-340 genes, leading to the characteristic symptoms observed in individuals with JBS
  • Alteration in the structure of chromosome 11, owing to a phenomenon called “unbalanced translocation”, in the parents
    • A parent carries gamete cells (egg or sperm) that have chromosomal rearrangement. There is exchange of parts between chromosome 11 and another chromosome, as a result of which there is no loss of genetic material in that individual. This is termed “balanced translocation”
    • This is often the case with the inherited cases of the disorder
    • Balanced translocations are not reported to cause serious health issues, although the balance could get lost in subsequent generations, in which case it is termed “unbalanced translocation”
  • Mosaicism, where an affected individual has a mixture of cells, some with and some without chromosome 11 alterations, which can result in less severe symptoms

What are the Signs and Symptoms of Jacobsen Syndrome?

The signs and symptoms of Jacobsen Syndrome are known to vary, depending on the size of genetic material lost from chromosome 11, as well as whether normal cells coexist with abnormal cells in an individual.

The signs and symptoms of Jacobsen Syndrome may include:

  • Abnormal facial features:
    • Small head (microcephaly)
    • Pointed forehead, narrow at temples (trigonocephaly)
    • Small ears which are low-set
    • Widely-spaced eyes (hypertelorism); droopy eyelids (ptosis)
    • Broad nose, nasal bridge
    • Abnormally thin upper lips
    • Excess skin covering in the inner corner of eyes (epicanthal folds)
  • Developmental delays:
    • Impaired motor skills and lack of coordination, leading to difficulties in sitting, standing and walking
    • Delay in speech
  • Vision defects such as outward squinting (strabismus), near- or far-sightedness
  • Feeding difficulties in infants
  • Immune insufficiency, leading to repeated ear and sinus infections, hearing problems, deafness (in some cases)
  • Bone deformities
  • Growth hormone deficiency, leading to a short stature
  • Problems with the gastrointestinal tract (GI tract), such as constipation
  • Kidney malfunction
  • Cognitive and behavioral issues, very similar to those observed in autism spectrum disorder:
    • Learning difficulties, delays
    • Easily distracted, with short attention spans
    • Compulsive behavior; hyperactivity
    • Lack of social and communication skills
  • Bleeding disorder or thrombocytopenia due to Paris-Trousseau syndrome.
    • Paris-Trousseau syndrome is considered to be a variant of Jacobsen Syndrome, wherein individuals have additional symptoms, such as abnormal bleeding, due to abnormal platelet function
    • An abnormality in platelets leads to impaired clotting, and renders the individuals susceptible to abnormal bleeding and bruising 
  • Heart abnormalities, owing to congenital heart disease
  • Genital defects, such as undescended testes in newborn boys

How is Jacobsen Syndrome Diagnosed?

An accurate diagnosis of Jacobsen Syndrome may be based on:

  • A thorough physical examination
  • An evaluation of family history
  • An assessment of symptoms, such as facial abnormalities, delays in reaching developmental milestones, abnormal bruising, behavioral problems and cognitive issues
  • Cytogenetic analysis to confirm clinical findings
  • In expecting parents, techniques such as fluorescence in-situ hybridization (FISH) and DNA microarray analysis on samples of amniocytes or chorionic villus, may detect Jacobsen Syndrome in the developing fetus

Genetic counsellors may help the prospective parents understand the consequences of such genetic changes in a child.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Jacobsen Syndrome?

The potential complications of Jacobsen Syndrome can include:

  • Increased susceptibility to a condition known as pyloric stenosis, in which an infant often vomits forcefully. This occurs as a result of a blockage between the stomach and intestines. Corrective surgery may be required to address this condition
  • Congenital heart defects, which might include a hole in the heart (ventricular septal defect) and abnormalities with the left side of the heart. Surgery may be required to correct these heart defects

How is Jacobsen Syndrome Treated?

The treatment for Jacobsen Syndrome often requires a team effort by medical professionals belonging to several disciplines in order to provide the affected children with a best quality of life. Depending on the severity and type of symptoms, the different treatment options might include:

  • For abnormalities of the GI tract: Insertion of a gastronomy tube (Gtube) to overcome feeding problems. The Gtube delivers food directly into the stomach
  • For abnormalities of the heart:
    • Monitoring heart function
    • Surgical repair of the heart defect
  • For abnormalities of the ear and sinuses:
    • Antibiotics for frequent bacterial infections
    • Hearing aids for hearing impairment
  • For hormonal defects:
    • Consultation with a pediatric endocrinologist
    • Growth hormone supplementation
  • For abnormal facial features:
    • Trigonocephaly may be corrected through surgery to open the cranial plates
    • Ptosis may be corrected through surgical lifting of the eyelids 
  • Abnormal vision may be rectified using corrective lenses
  • A consultation with a hematologist may be necessary to address blood clotting issues and bruises
  • Learning disabilities are treated through:
    • Speech therapy
    • Special education with visual aids and signs
    • Provision of a structured, ordered environment with set routines

How can Jacobsen Syndrome be Prevented?

  • Currently, there are no specific methods or guidelines to prevent Jacobsen syndrome, since it is a genetic condition
  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks prior to childbearing
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Jacobsen syndrome
  • Regular medical screening at periodic intervals with tests, and physical examinations are strongly recommended for individuals with this genetic disorder

What is the Prognosis of Jacobsen Syndrome? (Outcome/Resolutions)

  • The prognosis of Jacobsen Syndrome depends on the extent of genetic material lost, which in turn dictates the type and severity of symptoms in the affected individuals
  • Approximately 20% of children with Jacobsen Syndrome are reported to succumb to the disorder within the first 2 years of life
  • There are reports of some individuals who have lived beyond adolescence, and into adulthood

Additional and Relevant Useful Information for Jacobsen Syndrome:

Please visit our Congenital & Genetic Disorders Center for more physician-approved health information:

http://www.dovemed.com/diseases-conditions/congenital-genetic-disorders/

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: July 20, 2016
Last updated: July 20, 2016

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