XX male syndrome
Encyclopedia
XX male syndrome is a rare sex chromosomal disorder. Usually it is caused by unequal crossing over
between X
and Y chromosome
s during meiosis
in the father, which results in the X chromosome containing the normally-male SRY
gene. When this X combines with a normal X from the mother during fertilization, the result is an XX male.
This syndrome occurs in approximately four or five in 100,000 individuals, making it less common than Klinefelter syndrome.
. Individuals with this condition sometimes have feminine characteristics, with varying degrees of gynecomastia
but with no intra-abdominal Müllerian tissue
. According to research at the University of Oklahoma
health science centers, most XX males are not stereotypically feminine and are typical boys and men although other reports suggest that facial hair growth is usually poor and libido is diminished, with notable exceptions.
XX males have two X chromosomes, with one of them containing genetic material from the Y chromosome, making them phenotypically male; they are genetically female but otherwise appear to be male.
Chromosomal crossover
Chromosomal crossover is an exchange of genetic material between homologous chromosomes. It is one of the final phases of genetic recombination, which occurs during prophase I of meiosis in a process called synapsis. Synapsis begins before the synaptonemal complex develops, and is not completed...
between X
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
and Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
s during meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
in the father, which results in the X chromosome containing the normally-male SRY
SRY
SRY is a sex-determining gene on the Y chromosome in the therians .This intronless gene encodes a transcription factor that is a member of the SOX gene family of DNA-binding proteins...
gene. When this X combines with a normal X from the mother during fertilization, the result is an XX male.
This syndrome occurs in approximately four or five in 100,000 individuals, making it less common than Klinefelter syndrome.
Presentation
Symptoms usually include small testes and subjects are invariably sterileInfertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
. Individuals with this condition sometimes have feminine characteristics, with varying degrees of gynecomastia
Gynecomastia
Gynecomastia or Gynaecomastia, , is the abnormal development of large mammary glands in males resulting in breast enlargement. The term comes from the Greek γυνή gyné meaning "woman" and μαστός mastós meaning "breast"...
but with no intra-abdominal Müllerian tissue
Müllerian duct
Müllerian ducts are paired ducts of the embryo that run down the lateral sides of the urogenital ridge and terminate at the Müllerian eminence in the primitive urogenital sinus. In the female, they will develop to form the Fallopian tubes, uterus, cervix, and the upper two-third of the vagina; in...
. According to research at the University of Oklahoma
University of Oklahoma
The University of Oklahoma is a coeducational public research university located in Norman, Oklahoma. Founded in 1890, it existed in Oklahoma Territory near Indian Territory for 17 years before the two became the state of Oklahoma. the university had 29,931 students enrolled, most located at its...
health science centers, most XX males are not stereotypically feminine and are typical boys and men although other reports suggest that facial hair growth is usually poor and libido is diminished, with notable exceptions.
Clinical diagnosis
- Standard XX karyotypeKaryotypeA karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
in two tissues (with at least one, or both, containing the male SRYSRYSRY is a sex-determining gene on the Y chromosome in the therians .This intronless gene encodes a transcription factor that is a member of the SOX gene family of DNA-binding proteins...
gene) - Male external genitalia, sometimes showing hypospadiasHypospadiasHypospadias is a birth defect of the urethra in the male that involves an abnormally placed urinary meatus...
- Two testes which may or may not have descended the inguinal canalInguinal canalThe inguinal canal is a passage in the anterior abdominal wall which in men conveys the spermatic cord and in women the round ligament. The inguinal canal is larger and more prominent in men.-Site:...
. Most XX males have descended testes. - Absence of Müllerian tissue
Pathophysiology
Males typically have one X chromosome and one Y chromosome in each diploid cell of their bodies. Females typically have two X chromosomes.XX males have two X chromosomes, with one of them containing genetic material from the Y chromosome, making them phenotypically male; they are genetically female but otherwise appear to be male.
See also
- KaryotypeKaryotypeA karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
- Swyer syndromeSwyer syndromeSwyer syndrome, or XY gonadal dysgenesis, is a type of hypogonadism in a person whose karyotype is 46,XY. The person is externally female with streak gonads, and left untreated, will not experience puberty...
- X chromosomeX chromosomeThe X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
, for other diseases related to the X chromosome. - Androgen Insensitivity SyndromeAndrogen insensitivity syndromeAndrogen insensitivity syndrome is a condition that results in the partial or complete inability of the cell to respond to androgens. The unresponsiveness of the cell to the presence of androgenic hormones can impair or prevent the masculinization of male genitalia in the developing fetus, as...