Jacobsen Syndrome

What is Jacobsen Syndrome

Jacobsen syndrome or JBS, named after the Danish physician Petra Jacobsen who first identified and described it 1973, is a rare condition characterized by the loss of genetic material from the tip of the long arm (q) of chromosome 11. Hence, the condition is often called chromosome 11q deletion syndrome/disorder or partial 11q monosomy syndrome. The deletion size usually varies between 7 and 20 Mb while larger deletions may lead to disability to think and remember, behavioral issues, and other congenital defects.

What Causes Jacobsen Syndrome

It occurs due to the loss of several genes at the terminus of chromosome 11, which in most cases is brought about by a spontaneous mutation in parental sperm or egg, a random error in the formation of gametes, or a fault in cell division during fetal development. This deletion or loss of genetic materials is termed as de novo deletion. But, the triggering factors for such genetic changes are yet to be known.

Can it be Inherited

In rare cases, the deletion is inherited from a parent having balanced chromosomal translocation, a condition in which the genetic material is retained within the chromosome 11 even after the breakage of a part of the chromosome, which prevents any detectable abnormalities. In such cases, the parent is not affected by the disorder. However, a person with Jacobsen syndrome can also pass it on to his/her descendants.

Risk Factors

• Gender: Females are more at risk to develop the condition than males. The ratio of its occurrence between the two sexes is 2:1.
• Family history: About 15% of the people inherit Jacobsen syndrome from their parents.

Can Jacobsen Syndrome be Prevented

No specific guidelines exist for the prevention of Jacobsen syndrome. However, periodic medical screening tests may be performed if there are past occurrences in family members. Prenatal genetic testing of both the expectant parents and the fetus may be done to assess the risks during pregnancy.

Signs and Symptoms

Individuals with JBS may show wide-ranging symptoms, which are more severe in the case of larger deletions than the smaller ones. The following signs and symptoms have been reported in patients:

• Platelet dysfunction, pancytopenia or thrombocytopenia
• Speech and motor developmental delay
• Cognitive impairment along with learning difficulties
• Distinct facial features such as a large head (macrocephaly), prominent forehead (trigonocephaly), droopy eyelids (ptosis), wide-set eyes (hypertelorism), small, low-set ears, broad nasal bridge, upper eyelid skin fold (epicanthal folds) at the inner corner of the eyes, small lower jaw, and a thin upper lip
• Short height
• Sinus, ear infections, and hearing loss
• Feeding difficulties during early childhood
• Skeletal abnormalities

Complications

• Combined immunodeficiency characterized by recurrent infections
• Paris-Trousseau syndrome, a disorder of blood platelets, causing easy bruising and abnormal bleeding
• Attention-deficit hyperactivity disorder with behavioral issues like poor concentration and easy distractibility
• Autism characterized by inappropriate social interaction and impaired communication skills
• Compulsive behavior like shredding paper
• Congenital heart defects
• Kidney problems like double ureters, single kidney, and cysts in children
• Gastrointestinal disorders including pyloric stenosis, intestinal obstruction, constipation, and malformations of the GI tract affecting children

How is Jacobsen Syndrome Diagnosed?

After a complete physical examination, the family history of the patient is evaluated, and then the symptoms are assessed. Clinical tests to find out any intellectual deficit, or facial abnormalities, and low blood platelet count are used for making a diagnosis.

MRI, CT, or cerebral ultrasound may be done for finding out abnormalities of the brain. Laboratory findings are confirmed by cytogenetic analysis, including CGH+SNP microarray analysis.

Diagnosis in expecting parents involves procedures for analyzing samples of amniotic fluid or chorionic villus.

Differential Diagnosis

• Thrombocytopenia (platelet abnormality) caused by sepsis
• Turner syndrome
• Noonan syndrome
• Kabuki syndrome with symptoms like short stature, mental retardation, and abnormal palpebral fissures

Treatments for Jacobsen Syndrome

While there is no known cure for the condition, treatment is based on the symptoms present, with options including the following:

• For people affected by low platelet count, regular monitoring along with blood transfusions before or during surgical procedures may be required.
• Eye abnormalities and other visual problems may be improved with contact lenses, glasses, and surgery.
• Malformations of the kidney, urinary tract, and gastrointestinal tract, as well as abnormalities of bones, joints, muscles, and tendons, may be treated with surgery.
• Individuals affected by congenital heart defects may be treated with different medications. Infections of the respiratory tract or the heart’s valves and lining require high doses of intravenous antibiotic treatment before surgery.
• Patients with coordination and mobility issues may be treated with physical therapy for improving balance, posture, and strength.

Prognosis and Quality of Life

Medical therapy can address health complications and improve the overall health of an affected child, thus helping him or her to reach proper developmental milestones. Life expectancy of children born with Jacobsen syndrome is unknown. Some may die in their neonatal stage due to excessive bleeding and severe heart malformations while others may live into adulthood. The person recorded as having lived the longest with JBS lived for over 45 years of age. Finding support groups can help the parents and their child cope with the life threatening condition.

Incidence and Prevalence

It is estimated that 1 out of 100,000 newborns have chances of developing Jacobsen syndrome. According to recent population-based studies, over 200 individuals have been affected by this genetic condition.

ICD-9-CM and ICD-10-CM Codes

The ICD-9-CM code for JS is 758.3 while its ICD-10 code is Q93.5.