Terminal deletion

11q terminal deletion disorder is caused by the loss of genes from the end (terminus) of chromosome 11.

It is also called Jacobsen syndrome (JS) after the Danish researcher who first identified it in 1973.

Most of the affected persons in our network have this disorder. The genes lost from the end of the long arm of chromosome 11 determine most of the effects of Jacobsen syndrome. In most people, the chromosome has broken in the bands called 11q23 or 11q24 and the end is missing.

Some people have lost just a part of this area of the chromosome and they are expected to have some of the typical features but not all. The geneticist or paediatrician can tell you where your child's chromosome 11 has broken. In most people with Jacobsen syndrome, one chromosome 11 in each cell has the deletion but a few people have a mixture of cells with normal chromosomes.

This is called mosaicism and usually makes the disorder less severe. (Source: Unique's leaflet  "11q deletion disorder: Jacobsen syndrome" Opens external link in new windowwww.rarechromo.org)

Please see Dr Paul Grossfeld's Opens external link in new windowrecommendations for children with Jacobsen Syndrome for more information about baseline treatment. The recommendations are an extract from the article "Opens external link in new windowThe 11q Terminal Deletion Disorder: A Prospective Study of 110 Cases by Grossfeld et al." published in "American Journal of Medical Genetics 129A:51-61 (2004)"