Jacobsen’s Syndrome (11q Deletion or 11q-) is a rare chromesome disorder in which a portion of the 11th chromosome is missing. It affects about one in every 100,000 births. People who have this disorder may have heart problems, speech and language problems, specific facial characteristics, and mild to severe mental retardation, although many children with Jacobsen’s are extremely capable.

Jacobsen Syndrome is caused by the loss of a small portion of a chromosome at conception. A chromosome is made up of DNA code in a thread-like structure present in the nucleus of most cells in the body. The DNA code in turn carry genes which are the all important instructions about how each cell in the body should divide, grow and die. In each cell, there are 23 pairs of chromosomes. The body needs all 23 pairs for normal health and development. In Jacobsen Syndrome a small piece of the 11th chromosome is missing (or deleted) and this causes a range of clinical features in individuals with this condition. The features are related to the genes that are absent from the small piece of chromosome 11 that is missing. The reason for the loss of the piece of chromosome is not fully understood. Jacobsen syndrome tends to occur more frequently in females than in males.