In most cases, when children are conceived, they inherit a chromosome from each parent that helps to determine gender: X chromosomes are female and Y are male. The female child has two X chromosomes (XX), and the male child receives an X and Y chromosome (XY). In some circumstances, occurring in between 1 and 500 to 1000 births, a male child receives an extra X chromosome, creating an XXY chromosomal structure.
XXY chromosomes, or more accurately, the XXY chromosomal structure or pattern, when recognized, can create varied symptoms. These are not always expressed and the condition is not always recognized. The presence of the extra X may be called Klinefelter Syndrome, or boys with one are referred to as XXY males instead of describing their differences as a syndrome. It is important for people to remember that boys with an extra X chromosome may have all or none of the features associated with XXY males.
Some indications of the XXY chromosomal structure may be noticed in early childhood. These can include physical developmental delays, like walking or talking later than average. Speech difficulties may continue, and children may require speech therapy. Learning disabilities in early school, especially challenges with reading, can also affect some of these children. Boys with this additional X chromosome may also be more physically awkward and some are more shy or passive.
If XXY males are not diagnosed in childhood, is may be discovered during puberty. The testicles are usually small and do not increase in size, as they do with most boys during adolescence. Many males with this extra chromosome are infertile, though not all of them are. Though these children may actually be taller than most, they may lack the normal signs of developing puberty, and can have rounder bodies, more breast tissue, and scant to no development of body hair.
These children often benefit from testosterone treatment during puberty to help produce adolescent development of adult male features. Lack of this treatment does not mean that sexual behavior in life is impaired, however, and many XXY males have normal sexual lives in later life, though some men may note slightly less interest in sex. The XXY chromosome pattern does not predispose men to be “feminine” or to "develop" homosexuality. Studies on this suggest homosexuality is just as common in men who have the more common XY chromosome arrangement.
Diagnosis, especially for those who exhibit key symptoms, can be helpful. Boys who are not aware that there are physical reasons for slight differences between themselves and others may feel they are “weird” or “different.” Education, treatment with testosterone as needed, and support from parents can be a great help.
Supplementation with testosterone can also help lower risk of certain diseases later in life. For instance, men who do not get this help may have a higher rate of developing osteoporosis. They are also more likely to be at risk for breast cancer since they have slightly more breast tissue than the average male.