15q deletionsA chromosome 15q deletion is a rare genetic condition in which there is a missing copy of part of the genetic material that makes up one of the body’s 46 chromosomes. Like most other chromosome disorders, this increases the risk of birth defects, developmental delay and learning difficulties. However, the problems that can develop depend very much on what genetic material is missing.
15q deletions are caused by a mistake that occurs when the parents’ sperm or egg cells are formed. When egg and sperm cells are formed, the two members of each pair of chromosomes normally line up together and then break and recombine to create new chromosomes that contain different combinations of the genes transmitted by the grandparents to the parents of the child.
Children can be from all parts of the world and from all types of background have 15q deletions. No environmental, dietary or lifestyle factors are known to cause them. So there is nothing that either parent did before or during pregnancy that caused the deletion and equally nothing could have been done to prevent it.
If the deletion has arisen on the chromosome 15 that came from the father, the child will have Prader-Willi syndrome, characterised by overweight, overeating, small genitalia in boys and men, low muscle tone and dysfunction of the central nervous system. If the deletion has arisen on the chromosome 15 that came from the mother, the child will have Angelman syndrome, characterised by developmental delay, speech delay or no speech, a movement and balance disorder, an excitable personality and inappropriately happy disposition.
Where the deletion was smaller, some babies have apparently fed well and even breastfed and one child is described with an ‘immense appetite’. However, most babies have fed slowly, been unable to cope with breastfeeding but managed better with a bottle. All babies with a larger deletion are described as having feeding difficulties but with persistence these have resolved, generally without the need for long term tube feeding. Gastro oesophageal reflux (GORD, GERD), where the stomach contents return up the food passage, may occur.Children are generally sociable and affectionate and families find very great reward in their child being able to communicate his feelings towards them. As babies there seems to be a tendency to be passive and inert but by the preschool years a more ositive aspect generally emerges. Children usually do not understand safety constraints and need fulltime supervision.