Turner syndrome is caused by a problem with the X chromosome, usually when all or part of one X chromosome is missing or structurally altered in a baby’s cells.

What causes Turner syndrome?

In most people, each cell has 46 chromosomes, including two sex chromosomes: XX for females and XY for males. In Turner syndrome, a person is typically female but has only one working X chromosome instead of two, or part of the second X is missing or rearranged.

The main chromosome patterns that can cause Turner syndrome are:

  • Monosomy X (45,X) – Every cell has only one X chromosome and no second sex chromosome.
  • Mosaicism – Some cells have two X chromosomes, while others have only one X or an abnormal X.
  • Structural changes of the X chromosome – The second X may be partially missing, have a deleted short arm, form a ring, or have other structural abnormalities.
  • Rarely, Y‑chromosome material – A small piece of Y chromosome can be present where an X chromosome should be, which still leads to a Turner-like picture.

Because of this missing genetic material, development of the ovaries, growth, and some organs (like the heart and kidneys) is affected before and after birth.

How and when does this happen?

Turner syndrome almost always happens as a random event, not because of something the parents did or did not do.

  • During the formation of an egg or sperm, a chromosome can be lost due to an error in cell division called nondisjunction.
  • Sometimes the chromosomes are normal at conception, but the error occurs later, in the very early cell divisions of the developing embryo, which can cause mosaic Turner syndrome.

Doctors usually cannot identify a specific trigger or environmental cause (like diet, stress, or medications) in the parents; it is considered a sporadic chromosomal error.

Is Turner syndrome inherited?

Most cases are not inherited and do not “run in families.” Instead, they arise for the first time in that pregnancy because of the random chromosome error described above.

  • Very rarely, a structural X‑chromosome change may be passed down, but this is uncommon.
  • Parents of one child with Turner syndrome are usually not at high risk of having another child with the same condition, though a genetics team can give personalized risk information.

Quick FAQ style recap

  • What causes Turner syndrome?
    A missing or partially missing second sex chromosome (usually X) in some or all body cells.
  • Is it due to something a parent did?
    No; it almost always results from a random error in chromosome separation, not from lifestyle, behavior, or known exposures.
  • Is it inherited?
    Typically no. Most cases are sporadic and not passed from parent to child.

Bottom note: Turner syndrome and its causes are medical and genetic topics that should always be discussed with a healthcare professional or genetic counselor for personalized advice and testing options.

Information gathered from public forums or data available on the internet and portrayed here.