Chromosome Aberrations in Humans - Jacobsen Syndrome and Chromosome 11

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A Rare Disorder

Jacobsen syndrome is a rare genetic abnormality that is found in approximately 1 in 100,000 births. It is named for genetictist Dr. Petrea Jacobsen, who described the syndrome in 1973. A child born with Jacobsen syndrome will have a pear-shaped face. He or she will have learning difficulties that may range from mild to severe in some cases.The youngster may have language delays and may grow at a slower rate than would be expected in a normal child.

Congenital heart defects are not uncommon, and some of them may require surgery to correct. An individual with Jacobsen syndrome may bruise easily and and have difficulty getting bleeding stopped due to a low platelet count. People living with the syndrome are also prone to respiratory difficulties and gastrointestinal problems, such as deformities in the area leading from the stomach to the small intestine.


Jacobsen syndrome is caused by the lack of a small portion of a chromosome when conception occurs. Chromosomes contain the DNA code that determines how the cells in the body will grow and develop. Genes resemble a beaded necklace, and each cell normally contains 23 pairs of chromosomes. For a person with Jacobsen syndrome, a small portion of chromosome 11 is not present. The reason why a portion of this chromosome is missing is not known. The syndrome affects females more often than males.

Doctors are unable to diagnose the presence of Jacobsen Syndrome before birth. Since it is a rare condition, having a brother or a sister with Jacobsen’s doesn’t mean that other children in the family are at a higher risk of being born with this genetic defect.

Causes of Death Associated with Jacobsen Syndrome

A person with Jacobsen syndrome is at an increased risk of dying due to complications from a congenital heart defect or bleeding. Over time, treatment of congenital heart problems is improving, and so is the life expectancy for those born with this rare disorder.