Klinefelter's syndrome

Klinefelter's syndrome is the most common cause of male hypogonadism, occuring in 1-2 per 1000 male births. These patients have small, firm testes, are tall, and have behavioural problems, delayed speech and gynaecomastia. Testosterone therapy is sometimes used to improve the development of secondary sexual characteristics.

47 XXX (Triple X syndrome) is the presence of an extra X chromosome in females. Although some patients have mild learning disabilities, most do not have any unusual dysmorphic or medical problems, and are usually able to conceive. As such, triple X syndrome is rarely diagnosed.

The triploidies 69XXY, 69 XXX and 69 XYY result from fertilization of an egg by 2 sperm. They are estimated to occur in about 2% of conceptuses. Most affected babies are miscarried, although some live to be a few months of age.