Welcome to the second crash course on sex chromosome abnormalities
This time around we're going to be focussing on Klinefelter syndrome
Before we get into the specifics of Klinefelter syndrome
we're going to have a brief recap of the basics of chromosomes
For a more in-depth refresher, you can check out the first crash course on Turner syndrome, which is linked below
As a brief overview, in this video we will start with a recap of the basics about chromosomes
then discuss the basics of Klinefelter syndrome, including its prevalence and variations, then how it's diagnosed
We will then cover the symptoms and treatment for Klinefelter syndrome
We're going to wrap up by discussing where more research is needed
As a quick refresher, chromosomes are the instruction manuals inside each of our cells
They contain the genetic information that determines what individual cells and us, as whole people, become
The average person receives 23 chromosomes from their mom and 23 chromosomes from their dad
for a total of 46 chromosomes per cell
Two of these chromosomes are called the sex chromosomes and, as the name suggests, they determine the sex of an individual
The sex chromosomes can be either X or Y
Females typically have two X chromosomes, while males have one X and one Y chromosome
However, sometimes individuals end up with an abnormal number of chromosomes
One example of a chromosomal abnormality is Klinefelter syndrome
This syndrome is one of the most common sex chromosome disorders, affecting around 1 in 650 newborn boys
That's around 0.15% of all males
Individuals with Klinefelter syndrome appear male, but rather than the standard one Y and one X chromosome
they have one Y chromosome but more than one X chromosome
Most individuals with this syndrome have one Y and two X chromosomes
but some individuals have three or even four X chromosomes
Individuals might also have a combination of some cells with a normal X and Y and others with an abnormal number of sex chromosomes
this is called mosaicism
The syndrome occurs as a random error and is not an inherited condition
Risk factors for the condition are not increased by the actions of the parents as it's a random event
However, there is a higher risk for older mothers
There are two main tests used to diagnose Klinefelter syndrome: hormonal testing and chromosome analysis
In hormonal testing, blood or urine samples are analyzed to reveal the presence of abnormal hormone levels, including testosterone
For chromosome analysis, also known as a karyotype analysis,
a blood sample is sent to the lab to count the number of chromosomes and analyze their shapes
Most individuals with Klinefelter syndrome are actually never diagnosed with the condition
however, of the 25% who are diagnosed, a small percentage are diagnosed before birth
however, 90% are diagnosed after puberty, once the symptoms become more apparent
Now that we know the basics about Klinefelter syndrome
let's find out what symptoms individuals with Klinefelter syndrome have
Symptoms vary depending on how old the person is
As a baby, these individuals may have weak muscles
and take longer to reach the typical motor milestones like sitting up or crawling
Going into childhood, these individuals continue to have slower development of their motor skills, coordination, muscle strength and speed
and are typically taller than average
Additionally, around 75% of children with Klinefelter have learning disabilities as children
in particular, delayed speech and language acquisition
However, most adults with the syndrome have no speech difficulties
Many of the symptoms of Klinefelter syndrome arise at puberty
since individuals have lower levels of testosterone
These decreased levels disrupt normal development
including less body and facial hair, smaller testes, breast growth, and decreased muscle tone
In addition, the most significant symptom is infertility
which occurs in over 90% of individuals
Individuals with Klinefelter have increased risk for other conditions
including type 2 diabetes, cardiovascular disease and osteoporosis
Like the symptoms, treatment also varies based on the age of the individual
Across an individual's life there are a range of different healthcare professionals involved in treatment
including speech therapists, psychologists, general practitioners, pediatricians, and infertility specialists
In childhood, speech language pathologists, or speech therapists, are frequently involved in care
to address the language difficulties many children with Klinefelter syndrome face
Additionally, other rehabilitation specialists such as occupational or physical therapists
often assist with motor delays or other developmental difficulties
Other specialists such as counsellors, therapists, or educators, can also play a role depending on the child's individual needs
Once an individual reaches puberty, the most significant treatment is testosterone replacement therapy
to correct for the lower levels of testosterone
This helps ensure that individuals have proper sexual development, increased energy, improved mood, and helps individuals build relationships
When first beginning, there are check-ins with doctors every three months
to find out what dose of testosterone works best for them
and after that there are yearly check-ins
Testosterone replacement therapy is a life-long treatment
and also helps prevent some associated conditions, like osteoporosis and diabetes
Testosterone can be given in a range of ways, including via a pill, a gel, a patch, and an injection
Depending on which method is used, individuals receive the testosterone daily, such as with the pill or gel
or every 2 to 4 weeks or 3 to 4 months for injections
While there is a lot we know about Klinefelter, there is still much more to learn
One area for further research is testosterone replacement therapy
While there are known benefits associated with this treatment
there haven't been any large, randomized, placebo-controlled studies, which are the gold standard for scientific evidence
Some studies have shown benefits for starting treatment before puberty
so further research into when it is best to begin this treatment are still being conducted
Research is also needed to confirm the effects of testosterone replacement therapy on associated conditions, like osteoporosis
and provide insight into its impact on social and cognitive functions
It will also help reveal any potential negative or adverse effects of the treatment
Additionally, while most individuals with Klinefelter syndrome have reduced fertility
new technologies, like testicular sperm extraction (TESE), allow these individuals to have children
More evidence is being collected to determine what age sperm retrieval should be conducted at
since current evidence suggests that early retrieval is vital
Further research is also needed to determine if screening for Klinefelter syndrome should be introduced for all infants
since the appropriateness and cost of this level of screening is still undetermined
We hope you've learned something new about Klinefelter syndrome and other sex chromosome abnormalities
To keep on learning, check out other videos on the Demystifying Medicine channel