These are male individuals who present sexual chromatin and karyotype usually 47 XXY.
They constitute one of 700 to 800 male newborns, so it is one of the most common intersex conditions. Other less common karyotypes are 48 XXYY; 48 XXXY; 49 XXXYY and 49 XXXXY which respectively display 1, 2. and 3 barrels of Barr.
Although they may have an erection and ejaculation, they are sterile because their testicles are small and do not produce sperm due to atrophy of the seminiferous canals. Other features often present are: height, eunuch body, small penis, poor pubic hair and gynecomastia (breast enlargement).
In addition to these alterations of phenotypic sex, patients with Klinefelter's Syndrome show a marked decrease in intellectual level, the deeper the degree of polysomy.
Unlike Turner Syndrome, Klinefelter patients have immature and dependent personality development problems, probably due to their diminished verbal intelligence.
Until 1960, definitive evidence for diagnosis was provided by histological examination of the testicles, which, even after puberty, reveals absence of germ cells in the seminiferous canals; Rare are the cases of fertile Klinefelter that evidently have some normal sperm. Currently, Klinefelter identification is ensured by karyotype and sexual chromatin screening.
Triple X or Super Female Syndrome
Women with karyotype 47 XXX occur at a relatively high frequency: 1 case in approximately 700 births. They have normal phenotype, are fertile, but many have mild mental retardation. They feature Barr's corpuscle.
Women's cases 48 XXXX and 49 XXXXX They are rare and are characterized by increasing degrees of mental retardation.
Double Y or Super Male Syndrome
Karyotype individuals 47, XYY occur with the frequency of 1 case per 1,000 male births.
Although they are mostly normal men, early studies suggested that there was an extremely high frequency of mentally retarded patients with criminal records; Such studies revealed that about 2% of patients admitted to penal institutions and hospices had this karyotype, which showed that they were individuals XYY 20 times more inmates (instead of 1 per thousand, 2% corresponds to 20 per thousand) than in the free population.
However, the same data revealed that 96% of individuals XYY are normal. Thus, further research becomes necessary before relating this particular chromosomal constitution to certain abnormal behavioral traits; It is especially important to avoid a Naive interpretation related to a “crime chromosome”.
A very obvious physical characteristic of XYY is the tall stature as they usually have more than 180 cm ie. they are 15cm higher than the average of chromosomally normal male subjects.
We can suggest that genes located on the chromosome Y increase height and predispose its bearers to unexpected behaviors; in fact, the psychological profile of the individual XYY includes immaturity in emotional development and lower verbal intelligence, facts that can hinder your interpersonal relationship. A noteworthy fact is that institutionalized patients, both XY how XYY, exhibit an increased testosterone rate, which may be a contributing factor to antisocial inclination and increased aggression.