45,X/46,XY mosaicism

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45,X/46,XY mosaicism
Other names45,X0/46,XY MGD
SpecialtyObstetrics and gynaecology, endocrinology, medical genetics Edit this on Wikidata

45,X/46,XY

chromosomal disorder at birth, with an estimated incidence rate of about 1 in 15,000 live births.[2] Mosaic loss of the Y chromosome in previously non-mosaic men grows increasingly common with age.[3]

The clinical manifestations are highly variable, ranging from partial virilisation and ambiguous genitalia at birth, to patients with completely male or female gonads. Most individuals with this karyotype have apparently normal male genitalia, and a minority have female genitalia, with a significant number of individuals showing genital abnormalities or intersex characteristics.[4] A significantly higher than average number of other developmental abnormalities are also found in individuals with X0/XY mosaicism.[4] Psychomotor development is normal.

Signs and symptoms

Conditions can be distinguished histologically and by

mosaicism.[7] The most common presentation of 45,X/46,XY karyotype is phenotypically normal male, next being genital ambiguity.[8]

There is a range of chromosomal anomalies within 45,X/46,XY where the variations are very complex, and the actual result in living individuals is often not a simple picture.

SHOX gene is commonly associated with short stature.[9] Psychomotor development is normal.[citation needed
]

As the gonads may not be symmetrical, the development of the

Wolffian duct may be asymmetrical, too.[10] Because of the presence of dysgenetic gonadal tissue and Y chromosome material, there is a high risk of the development of a gonadoblastoma.[1]

Causes

In a normal situation, all the cells in an individual will have 46 chromosomes, with one being an X and one a Y or with two Xs. However, sometimes during the early copying processes of DNA replication and cell division, one chromosome can be lost. In 45,X/46,XY, most or all of the Y chromosome is lost in one of the newly created cells. All the cells then made from this cell will lack the Y chromosome. All the cells created from the cells that have not lost the Y chromosome will be XY.[11] The 46,XY cells will continue to multiply at the same time as the 45,X cells multiply. The embryo, then the fetus, and then eventually the baby will have what is known as a 45,X/46,XY constitution.

There are many chromosomal variations that cause the 45,X/46,XY karyotype, including malformation (isodicentricism) of the Y chromosomes, deletions of Y chromosome or

SRY gene which may lead to abnormal genitals and testosterone levels.[citation needed][original research?
]

Diagnosis

Identification of 45,X/46,XY karyotype has significant clinical implications due to known effects on growth, hormonal balance, gonadal development and histology.[2] 45,X/46,XY is diagnosed by examining the chromosomes in a blood sample.

The age of diagnosis varies depending on manifestations of disease prompting reason for

cytogenetic testing. Many patients are diagnosed prenatally due to fetal factors (increased nuchal fold, or abnormal levels of serum), maternal age or abnormal ultrasounds, while others will be diagnosed postnatal due to external genital malformation.[2] It is not uncommon for patients to be diagnosed later in life due to short stature or delayed puberty, or a combination of both.[8]

45,X/46,XY mosaicism can be detected prenatally through amniocentesis however, it was determined that the proportion of 45,X cells in the amniotic fluid cannot predict any phenotypic outcomes, often making prenatal genetic counselling difficult.[6]

Management

See also

References

  1. ^ a b c [1][permanent dead link] "45,X/46,XY including Y chromosome rearrangements". (PDF) Rarechromo.org
  2. ^
    PMID 22605431
    .
  3. PMID 27064253
    .
  4. ^
    PMID 2294747
    .
  5. PMID 12379746
    .
  6. ^
    S2CID 20193032
    .
  7. ^ Chang, H J; et al. (1990). "The phenotype of 45,X/46,XY mosaicism: an analysis of 92 prenatally diagnosed cases". American journal of human genetics vol. 46 (1): 5 – via National Library of Medicine.
  8. ^
    PMID 23422775
    .
  9. ^ 45,X/46,XY mixed gonadal dysgenesis. Orfa.net; August 2015.
  10. PMID 480090
    .
  11. ^ 45,X/46,XY Mosaicism: Report of 27 Cases. Pediatrics Vol. 104 No. 2 August 1, 1999. pp. 304 -308

External links

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