Turner syndrome (TS) is a DSD that describes a partial or full loss of the second sex chromosome, usually resulting in particular phenotypic presentations and a distinct physical appearance. Though Turner syndrome can present in many ways for many different people for different reasons. We will explore the different variations TS has on this page!
When some people think of Turner syndrome, they usually associate the condition with a predominantly female phenotype (vulva, mullerian structures, dysgenic/hypoplastic ovaries or streak gonads, etc). And while a predominantly female sexual phenotype is most common in TS with full (see next section) or partial (see last section) second chromosome loss without any Y chromosome material or other sex determinant gene differences, people with male TS are also a prevalent minority!
You may be thinking, “Well, what is male Turner syndrome?”
“Male Turner syndrome” would usually describe a 5 sex characteristics presentation something along the lines of:
45, X0/46, XY chromosomal makeup Bilateral testes (one or both may be partially dysgenic, or one may be a streak or absent respectively [monorchia]) Prostate, seminal vesicles (may be underdeveloped), may have some mullerian structures (EX: part of or an underdeveloped uterus or cervix) Penis, scrotum (male genitalia), may have some genital differences (Micropenis, hypospadias) or may have genital ambiguity (link) Usually testosterone dominant, though may have lowered testosterone production
Alongside some the non-sex related phenotypes and physical differences that may be associated with Turner syndrome, such as:
Due to both the partial loss of the second sex chromosome, and partial retention of the Y chromosome and SRY gene, a person who has male Turner syndrome will have the non-sexual phenotype associated with TS, while still having only testicular tissue. And due to only having testes or a testis, most people with male TS will either have a full, or partially incomplete male puberty if they have gonadal insufficiency/hypoplasia or dysgenesis.
Yes, some people will have partial Y loss that does not present as chromosomal mosaicism. Some people might have a deletion to the long or short arm of the Y chromosome, or a ring Y chromosome and present with the Male TS phenotype. And occasionally people with female or female-leaning external genitals will present with an otherwise male TS phenotype.
Yes! Some people will have a mixed gonadal dysgenesis phenotype or a partial gonadal dysgenesis phenotype without the TS physical differences, or will have the sex characteristics more common in other forms of partial monosomy X.
Some people with male TS can produce sperm and are fertile naturally, others may have more difficulty with sperm production and may seek medical assistance, and others may be mostly or completely infertile.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1792467/
https://jimdc.org.pk/jimdc/Volumes/1-4/12_Male%20with%20Deletion%20of%20Long%20Arm%20of%20Y%20chromosome%20A%20Rare%20Cause%20for%20Ambiguous%20Gender.pdf
https://scholarlyexchange.childrensmercy.org/researchdays/GME_Research_Days_2021/researchday4/12/
https://www.rarechromo.org/media/information/Chromosome_Y/45X%2046XY%20%20including%20Y%20chromosome%20rearrangements%20FTNP.pdf
Full Monosomy X Turner syndrome may be a more familiar variation of TS to some. People with a complete loss of the second sex chromosome, or full monosomy X Turner syndrome, will usually have the following 5 sex characteristics:
Because of the gonadal dysgenesis that people with full monosomy X TS have, their mullerian structures are usually underdeveloped mostly as a result of low estrogen and progesterone production. Because of their streak gonads or dysgenic ovaries, most people with full monosomy X TS do not develop at all upon puberty. Though there is often some auxiliary hair growth and sometimes tanner grade 1 breast development. There is usually no naturally occurring menstruation in full monosomy X TS because of the degree of gonadal dysgenesis. Though with hormonal supplementation of estrogen and/or progesterone, many people with full monosomy X TS can and do menstruate.
All people with full monosomy X TS will usually present with some of the following non-sexual physical differences:
It is a somewhat common misconception that most people with full monosomy X TS have intellectual disability. While people with full monosomy X TS may be more disposed to things like speech delay or learning difficulties as compared to the general population, it is a minority of people with full monosomy X TS that have an intellectual disability. Though of course, it is important to be considerate and respectful of people in general, no matter their intellectual capabilities.
Yes! Some people with full monosomy X TS will have hypoplastic ovaries as opposed to streak gonads or dysgenic ovaries. Usually people with hypoplastic ovaries or generally less gonadal dysgenesis will produce more sex hormones come puberty. It is uncommon for anybody with full monosomy X TS to naturally experience a full female puberty, but people with less ovarian dysgenesis can experience some more secondary sex development. Such as more breast growth, auxiliary hair growth, and in some menstruation.
https://karger.com/hrp/article/89/2/90/162719/Prediction-of-Spontaneous-Puberty-in-Turner
Usually people with full monosomy X TS are infertile and are unable to conceive without medical assistance. Sometimes Oocyte cryopreservation is possible, though often proves challenging. Though ovarian tissue cryopreservation is a promising upcoming development as a fertility option for people with full monosomy X TS. And of course, oocyte/egg donation/implantation, or embryo implantation has proven successful in people with full monosomy X TS who desire to carry a child.
While generally people with an 45, X0 chromosomal makeup have a predominantly female phenotype, there are some people with predominantly male phenotypes! Usually this is due to SRY translocation, and/or a very small part of the Y chromosome being translocated (attached) to another chromosome. In this presentation, the SRY gene and/or Y chromosome material triggers the development of testes, and subsequent male external genitalia.
Another common variation of Turner syndrome is partial monosomy X Turner syndrome! Similarly to male Turner syndrome, the second sex chromosome is partially, but not fully lost. Differently from male TS, partial monosomy X TS retains some of the second X chromosome, whereas in male TS some of the Y chromosome is retained.
Partial monosomy X TS can have a degree of presentation! Difference in presentation from person to person is often due to the amount of cells within the body that have an 45, X0 or 46, XX chromosomal makeup respectively. Depending on how many of the body’s cell are 45, X0, and depending on how many of the body’s cells 46, XX, and where each of either cell makeup is most concentrated, can and will produce some differences.
We can get back to the cells later! Despite the variation in presentation we can see in partial monosomy X TS, usually the 5 sex characteristics will be something like: