What causes Turner syndrome ?
What causes Turner syndrome? Turner syndrome is caused by partial or complete loss of one of the X chromosomes in cells of females. Females without Turner syndrome have 2 full X chromosome in all of their cells (and males have one X chromosome and one Y chromosome). The missing genetic material affects development before and after birth. Most females with Turner syndrome are missing a full X chromosome in all of their cells (also called monosomy X). This form results from a random error in an egg or sperm cell prior to conception. Some females with Turner syndrome have two X chromosomes, but one of them is missing a piece (has a deletion). Depending on the specific gene(s) that are missing, the features of Turner syndrome may result. A deletion may occur sporadically (not inherited) or may be inherited from a parent. Mosaic Turner syndrome (when some cells have one X chromosome and some have two sex chromosomes) is caused by a random error in early fetal development (shortly after conception). It is still unclear exactly which genes on the X chromosome are associated with each feature of Turner syndrome. It is known that the SHOX gene on the X chromosome is important for growth and bone development. A missing copy of this gene is thought to result in the short stature and skeletal abnormalities in many affected women.