Klinefelter Syndrome

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Introduction

Klinefelter syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. Klinefelter syndrome is a genetic condition affecting males, and it often isn't diagnosed until adulthood.

Klinefelter syndrome may adversely affect testicular growth, resulting in smaller than normal testicles, which can lead to lower production of testosterone. The syndrome may also cause reduced muscle mass, reduced body and facial hair, and enlarged breast tissue. The effects of Klinefelter syndrome vary, and not everyone has the same signs and symptoms.

Most men with Klinefelter syndrome produce little or no sperm, but assisted reproductive procedures may make it possible for some men with Klinefelter syndrome to father children.

Causes

Klinefelter syndrome occurs as a result of a random error that causes a male to be born with an extra sex chromosome. It isn't an inherited condition.

Most often, Klinefelter syndrome is caused by a single extra copy of the X chromosome, resulting in a total of 47 chromosomes per cell. Males normally have one X chromosome and one Y chromosome in each cell (46, XY), while females have two X chromosomes (46, XX).

- An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain one or more extra copies of the X chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have one extra copy of the X chromosome in each cell (XXY), the most common cause, or more extra X chromosomes in each of the body's cells which is rare and known as "variants of Klinefelter syndrome(48,XXXY, 48,XXYY and 49,XXXXY) and results in a severe form .

- People with Klinefelter syndrome usually have two X chromosomes and one Y chromosome (47, XXY). Some people with Klinefelter syndrome have the extra X chromosome in only some of their cells; these people are said to have mosaic Klinefelter syndrome, with fewer symptoms.

It is estimated that about half of the time, the cell division error occurs during development of the sperm, while the remainder are due to errors in egg development. Women who have pregnancies after age 35 have a slightly increased chance of having offspring with this syndrome.

Incidence

It is estimated that 1 in every 500 to 1,000 newborn males has an extra X chromosome, making Klinefelter syndrome one of the most common chromosomal disorders seen among newborns. Variants of Klinefelter syndrome (such as 48,XXXY, 49,XXXXY) are much rarer, occurring in 1 in 50,000 to 1 in 85,000 or fewer newborns.

Other Medical or Scientific Names

-   47,XXY 
-   XXY syndrome or condition
-   XXY trisomy
-   47,XXY/46,XY or mosaic syndrome (rare variation)
-   Poly-X Klinefelter syndrome, including the following rare variations: 
      * 48,XXYY (or tetrasomy)
      * 48,XXXY (or tetrasomy)
       *49,XXXXY (or pentasomy)

Signs and Symptoms

The signs and symptoms vary among affected people. Some men with KS have no symptoms of the condition or are only mildy affected. In these cases, they may not even know that they are affected by KS. When present, symptoms may include:[1][2][3]

   Small, firm testicles
   Delayed or incomplete puberty with lack of secondary sexual characteristics resulting in sparse facial, body, or sexual hair a high-pitched voice and body fat distribution resulting in a rounder, lower half of the body, with more fat deposited in the hips, buttocks and thigh instead of around the chest and abdomen
   Breast growth (gynecomastia)
   Reduced facial and body hair
   Infertility
   Tall stature
   Abnormal body proportions (long legs, short trunk, shoulder equal to hip size)
   Learning disablity
   Speech delay
   Crypthochirdism
   Opening (meatus) of the urethra (the tube that carries urine and sperm through the penis to the outside) on the underside of the penis (hypospadias) instead of the tip of the head of the penis
   Social, psychologic and behavioral problems  

Whether or not a male with KS has visible symptoms depends on many factors, including how much testosterone his body makes, if he is mosaic (with both XY and XXY cells), and his age when the condition is diagnosed and treated.[1] Some people have a slightly increased risk of developing breast cancer, a rare extragonadal germ cell tumor, lung disease, varicose veins and osteoporosis as well as some autoimmune disorders such as systemic lupus erythematosus, rheumatoid arthritis and Sjogren's syndrome.[2][4]

Some people with features of Klinefelter syndrome have more than one extra X chromosome in each cell (such as 48,XXXY or 49,XXXXY). In these cases, known as "variants of Klinefelter syndrome", the signs and symptoms can be more severe and may include:[1][2][4]

   Intellectual disability
   Distinctive facial features
   Skeletal abnormalities
   Poor coordination
   Severe speech difficulties
   Behavioral problems
   Heart defects
   Teeth problems.

Diagnostic Procedures

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Outcome Measures

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Management / Interventions

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Differential Diagnosis

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Resources

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References

Myśliwiec, Andrzej & Knapik, Henryk & Pasek, Angelika & Kuszewski, Michał & Saulicz, Mariola & Ryngier, Paweł & Wolny, Tomasz. (2011). REHABILITATION OF PATIENTS WITH THE KLINEFELTER’S SYNDROME - REVIEW OF AVAILABLE LITERATURE.

https://rarediseases.info.nih.gov/diseases/8705/klinefelter-syndrome#ref_846

https://www.nichd.nih.gov/health/topics/klinefelter

https://www.ncbi.nlm.nih.gov/gtr/conditions/C0022735/?_ga=2.249310535.1187197716.1601932924-37510577.1601932924

https://www.youtube.com/watch?v=R-jqm7KXd0s&has_verified=1