Sex chromosome abnormalities are gender specific. Female abnormalities are due to variation in number of X chromosome .Male abnormalities are due to either the X or the Y chromosome or both.
Sex Chromosomal abnormalities
- Turner’s syndrome
- Klinefelter’s syndrome
- Triple X syndrome
- Testicular feminizing syndrome
- True hermaphrodites
- Developmental abnormalities
1.TURNER’S SYNDROME:- Turner ,s syndrome is also known as gonadal or ovarian dysgenesis. This is a condition that affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing. Turner syndrome can cause a variety of medical and developmental problems. In This case Karyotype is 45 XO (44 autosome + 1 sex chromosome).This is results from nondisjunction of one X chromosome.
- Diminish sexual development.
- Webbing of neck.
- Gonadal tissue absent or rudimentary.
- Primary amenorrhea.
- No sexual maturation at puberty.
2.Klinefelter’s syndrome:- This is also known as SEMINIFEROUS TUBULE DYSGENESIS. This syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. It is a condition affecting males, and it often isn’t diagnosed until adulthood This is Most common sex chromosomal abnormality . Karyotype is 47 XXY (44 autosome + XX sex chromosome +one extra Y chromosome)
- Feminine feature in an apparent male with small testis.
- Patient is genetically female but develop male genitalia.
- Male characteristics develop due to adequate testosterone
- Mental retardation
- Primary hypogonadism and infertility
- Seminiferous tubules are not properly develop
3.Triple x syndrome:-This is a common aberration of sexual differentiation in which the karyotype is XXX .Usually, it is not associated with any characteristic abnormalities and therefore remains undetected.In this case Females are known as super females.
- Taller than the average height.
- Ovary abnormalities lead to premature ovarian failure.
- Learning difficulties in speech and language.
- In the range of low or normal intelligence.
4.TESTICULAR FEMINIZATION SYNDROME:- The patient appear normal females externally. The chromosome are 46 in number with XY KARYOTYPE. This is a X-Linked recessive disorder. These are the Androgen receptor resistance-high testosterone blood level.
- Patient is genetically male but appears like normal female.
- Primary amenorrhea.
- no development of uterus.
- Gonads are testis with immature seminiferous tubule.
- Testis are present but spermatogenesis does not occur.
5.TRUE HERMAPHRODITISM:-This is a rare condition in which both testis and ovaries are present.In this case karyotype is 46 (XX-XY).Sometimes , ovary is present on one side and testis is present on the opposite side. Both male and female sex differentiations occur with development of combined female & male external and internal genitalia.
6.PSEUDOHERMAPHRODITISM:-A pseudo hermaphrodite is an individual with genetic constitution and gonad of one sex , but the external genitalia of other sex .Patients have normal gonadal development according to their chromosome. Both male and female pseudo hermaphrodite are present.
1.Female pseudo hermaphroditism-
- Male external genital develop in genetic female.
- Individual posses ovary and oviduct with varying degree of masculine differentiation.
- Source of androgen is congenital virilising adrenal hyperplasia.
- Chromosomal sex is female.
2.Male pseudo hermaphroditism-
- Development of female external genitalia in genetic male.
- Due to defective testicular development.
- Also due to androgen resistance or due to defect in androgen receptor.
Diagnosis of Sex Chromosomal abnormalities-Chromosomal abnormality can be diagnosed before birth by-
- Chorionic villi sampling
- Triple marker screening test
1.Amniocentesis– It is a procedure in which amniotic fluid is removed from the uterus for testing or treatment. Amniotic fluid is the fluid that surrounds and protects a baby during pregnancy. This fluid contains fetal cells and various proteins.
2.Chorionic villus sampling (CVS)– It is a prenatal test in which a sample of chorionic villi is removed from the placenta for testing. The sample can be taken through the cervix (trans cervical) or the abdominal wall (transabdominal).
- 3.Triple marker screening test- This is also knows as triple test or triple screen, the Kettering test or the Bart’s test. This is an investigation performed during second trimester of pregnancy to classify a patient as either high-risk or low-risk for chromosomal abnormalities (and neural tube defects). Triple marker screening test is used to measure the 3 substance
- Alpha- fetoprotein
- Human chorionic gonadotrophin
Sex chromosomal abnormalities are rare seen in human population.Chromosomal error prevent a foetus from developing normally and because of this abnormality miscarraige occur in 1st trimester of pregnancy