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June 12, 2022

Kallmann Syndrome vs Klinefelter Syndrome

Kallmann Syndrome versus Klinefelter syndrome

In our previous articles, we have discussed Kallman syndrome. It is sometimes confused with Klinefelter syndrome. Today we are going to compare these two conditions; Kallmann syndrome versus Klinefelter syndrome.

Kallmann syndrome vs Klinefelter syndrome
Photo courtesy of Pixabay

What is Klinefelter syndrome?

Klinefelter syndrome is a genetic condition that results when a male is born with an extra copy of the X chromosome.  It shares similarities with Kallmann syndrome, but there are important differences between these two genetic conditions.

The three main differences between Klinefelter and Kallmann syndrome is Klinefelter only affects males. Kallmann can affect both males and females but affects 5 times as many males as females.  While both are genetic conditions, Klinefelter syndrome is not inherited and Kallmann syndrome is.  Klinefelter is the result of a random error in which a male is born with an extra X chromosome. Klinefelter syndrome is far more common than Kallmann syndrome. Klinefelter syndrome affects 1 in 500 males while Kallmann syndrome affects 1 in 8,000 males. This link reviews the statistics related to Klinefelter syndrome in detail.

Both are associated with low testosterone levels.

Signs and Symptoms of Klinefelter Syndrome

Signs and symptoms of Klinefelter syndrome vary by the age of the male.

Signs and symptoms may include:


  • Weak muscles
  • Delayed motor development such as sitting, crawling, and walking
  • Delay in speaking
  • Undescended testicles at birth

Boys and teenagers

Signs and symptoms may include:

  • Taller than average stature
  • Longer legs, shorter torso, and broader hips compared with other boys
  • Absent, delayed, or incomplete puberty
  • Less muscle and less facial and body hair compared with other teens after puberty
  • Small and firm testicles
  • Small penis
  • Enlarged breast tissue (gynecomastia)
  • Weak bones (due to low testosterone levels)
  • Low energy levels
  • Tendency to be shy and sensitive
  • Difficulty expressing thoughts and feelings or socializing
  • Problems with reading, writing, spelling, or math


Signs and symptoms may include:

  • Low sperm count or no sperm
  • Small testicles and penis
  • Low sex drive
  • Taller than average height
  • Weak bones
  • Decreased facial and body hair
  • Less muscle compared with other men
  • Enlarged breast tissue or gynecomastia
  • Increased belly fat

Complications of Klinefelter Syndrome

Many men with Klinefelter syndrome are only diagnosed after they are found to have an infertility issue.  To avoid this delay in diagnosis consider the diagnosis if several of the signs and symptoms above are present.

Klinefelter individuals have a higher risk of developing breast cancer than other males.  Also, 10% of Klinefelter individuals fall on the autism spectrum and on average have IQs 10-15 points lower than average. Life expectancy is normal in Klinefelter syndrome.

Other complications or risks related to Klinefelter syndrome include:

  • Anxiety and depression
  • Social, emotional, and behavioral problems including low self-esteem and emotional immaturity
  • Weak bones (osteoporosis) are related to low testosterone levels.
  • Heart and blood vessel disease
  • Lung disease
  • Metabolic syndrome includes type 2 diabetes, high blood pressure (hypertension), and high cholesterol and triglycerides (hyperlipidemia)
  • Autoimmune disorders such as lupus and rheumatoid arthritis
  • Tooth and oral problems that make dental cavities more likely

Klinefelter syndrome is the result of a random error that causes a male to be born with an extra sex chromosome. It isn’t an inherited condition in contrast to Kallmann syndrome.

Humans have 46 chromosomes, including two sex chromosomes that determine a person’s sex. Females have two X sex chromosomes (XX). Males have an X and a Y sex chromosome (XY). Klinefelter syndrome stems from a random genetic event. There is less than a 1% chance for other children in the family to be diagnosed with Klinefelter syndrome if one child has it already

Klinefelter syndrome can be caused by:

  • One extra copy of the X chromosome in each cell (XXY), the most common cause
  • An extra X chromosome in some of the cells (mosaic Klinefelter syndrome), with fewer symptoms
  • More than one extra copy of the X chromosome, which is rare and results in a severe form

Extra copies of genes on the X chromosome interfere with male sexual development and fertility.


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Dr. Joe Jacko

Dr. Joe is board certified in internal medicine and sports medicine with additional training in hormone replacement therapy and regenerative medicine. He has trained or practiced at leading institutions including the Hughston Clinic, Cooper Clinic, Steadman-Hawkins Clinic of the Carolinas, and Cenegenics. He currently practices in Columbus, Ohio at Grandview Primary Care. Read more about Dr. Joe Jacko

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