Males with Klinefelter syndrome have XXY chromosomes, rather than XY chromosomes, leading to a lower level of the male hormone testosterone and related symptoms.
The symptoms are often subtle in infancy and childhood and may go unnoticed until the individual reaches puberty and adulthood. In many cases, the condition is not diagnosed until the man wishes to have a child, but struggles with infertility. However, it can have a profound effect on the growth or appearance of some boys, even from a young age.
Signs of Klinefelter syndrome in infants are often subtle and may not be reported to a medical professional by parents or caregivers. They may include:
- Weak muscles
- Delayed motor skill development (e.g. learning to sit, crawl and walk)
- Delayed speech development
- Quiet personality and character
- Undescended testicles at birth
At this age, the syndrome does not usually have a profound effect on the growth and development. For this reason, it can often be mistaken as the normal variance of growth in infants.
Childhood and Adolescence
Slow or delayed body development during childhood is a common sign that prompts parents to seek medical advice for their son. The signs and symptoms of Klinefelter syndrome in young boys and teenagers may include:
- Tall stature (long legs, short torso and broader hips)
- Small penis
- Small, firm testicles
- Gynecomastia (enlarged breast tissue)
- Weak bones
- Shyness or quiet character
Puberty may be absent, delayed or incomplete. In respect to other boys after puberty, males affected by Klinefelter syndrome tend to have less muscle mass and facial or body hair.
Boys with Klinefelter syndrome also tend to have difficulty socializing, interacting with others and expressing their feelings. The may have a short attention span and struggle with activities such as reading, writing, spelling and mathematical calculations.
Men with Klinefelter syndrome may be affected by:
- Small testicles and penis
- Tall stature
- Low bone density
- Less facial and body hair than usual
- Enlarged breast tissue
- Low libido
For many men, infertility is the first sign that prompts them to seek medical advice about the condition. If regular, unprotected sex is engaged for a year without a pregnancy, this is a good sign to see a doctor and investigate the cause of infertility. There are many possible conditions that may cause infertility in males and Klinefelter syndrome is just one possible explanation.
Rationale of Symptoms
The symptoms of Klinefelter syndrome are linked to the low levels of testosterone in the body, due to the additional X chromosome. The severity of symptoms depends on the level of testosterone required at each developmental stage and the available stores in the body.
It is for this reason that symptoms are subtle during the early years of life. The need for testosterone is low and the reduced levels do not have a significant impact on the learning and development of the individual.
However, as the boy reaches the age of puberty, the demand for testosterone increases. This results in abnormal growth and development of boys that are usually regulated by testosterone, such as genital growth, pubic hair, muscle growth, libido and fertility.