Turner syndrome pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Akash Daswaney, M.B.B.S[2]


Humans have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. Two of these chromosomes, the sex chromosomes, determine if you become a boy or a girl. Loss the paternally or maternally derived X chromosome would lead to the class 45 XO karyotype. Sometimes, an individual may have two cells lines with different genetic makeups. The percentage of this mosaicism is said to determine the severity of the phenotype in the patient. Structural abnormalities such as the formation of a ring chromosome or an isochromosome and other mechanisms such as lyonization or imprinting also play a role in the pathophysiology of Turner Syndrome.




Chromosomal structure

Nonfunctional Y


  • Each of the causes mentioned above can occur as a mosaicism, that is, some of the cells carry the mutation and some don't. That is, two cell lines of different genetic make ups exist.
  • This happens if the error takes place in one cell after the very first divisions of the early embryo after fertilization.
  • The exact mixture of the two different cell types depends on when the nondisjunction occurred. *However, if the nondisjunction occurs after enough divisions, the fraction of abnormal cells is probably not large enough to show any significant effects.
  • For instance, such a 45,X/46,XY individual will develop as a male, without Turner syndrome.
    • It is hypothesized that lower the percentage of mosaicism, the lesser is the phenotype expression.
  • Mosaicism is found in about 20% of individuals with Turner syndrome.

No single Y



  • Imprinting is an alteration in the expression of a gene, depending on whether it has been inherited from the mother or father.
  • In the case of imprinting, it is not known whether there is a specific correlation between retention of the maternal or paternal chromosome and expression of particular phenotype.


  1. 1.0 1.1 Sybert VP, McCauley E (2004). "Turner's syndrome". N Engl J Med. 351 (12): 1227–38. doi:10.1056/NEJMra030360. PMID 15371580.
  2. Cui X, Cui Y, Shi L, Luan J, Zhou X, Han J (2018). "A basic understanding of Turner syndrome: Incidence, complications, diagnosis, and treatment". Intractable Rare Dis Res. 7 (4): 223–228. doi:10.5582/irdr.2017.01056. PMC 6290843. PMID 30560013.
  3. 3.0 3.1 Kesler SR (2007). "Turner syndrome". Child Adolesc Psychiatr Clin N Am. 16 (3): 709–22. doi:10.1016/j.chc.2007.02.004. PMC 2023872. PMID 17562588.
  4. Frías JL, Davenport ML, Committee on Genetics and Section on Endocrinology (2003). "Health supervision for children with Turner syndrome". Pediatrics. 111 (3): 692–702. doi:10.1542/peds.111.3.692. PMID 12612263.
  5. Collett-Solberg PF, Gallicchio CT, Coelho SC, Siqueira RA, Alves ST, Guimarães MM (2011). "Endocrine diseases, perspectives and care in Turner syndrome". Arq Bras Endocrinol Metabol. 55 (8): 550–8. doi:10.1590/s0004-27302011000800008. PMID 22218436.

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