About kennedy-stefanis disease

What is kennedy-stefanis disease?

Kennedy disease is a rare, X-linked slowly progressive neuro-muscular disorder. Kennedy disease is typically an adult-onset disease, where symptoms occur mainly between the ages of 20 and 50. The disease is characterized by symptoms such as muscle weakness and cramps in the arms, legs, and facial area, enlarged breasts, and difficulty with speaking and swallowing (dysphagia). Kennedy disease affects fewer than 1 in 150,000 males and does not typically occur in females, who are protected by their low levels of circulating testosterone, accounting for the sex-limited inheritance pattern in this disorder. Treatment is symptomatic and supportive and life expectancy is normal, though a small percentage of patients (~ 10%) succumb to the disease in their 60's or 70's.

Kennedy disease is named after William R. Kennedy, MD, who described this condition in an abstract in 1966 and a full report in 1968.

What are the symptoms for kennedy-stefanis disease?

Most people who develop SBMA are assigned male at birth, or have XY chromosomes. Usually they experience onset of the disease between the ages of 30 and 50. However, SBMA can also show up in the teen years and later in life.

Early symptoms usually include falling down, and struggling to walk or control muscles.

Other hallmark symptoms include:

AsSBMA progresses, muscles in the hands and face (including the tongue) may twitch. Eventually, the nerves that control certain muscles start to die, leaving the muscles unable to contract. This causes Numbness and weakness.

In some cases, one side of the body is more affected than the other.

What are the causes for kennedy-stefanis disease?

SBMA is an inherited condition, caused by an X chromosome defect.

The mutation in a section of DNA is called a CAG trinucleotide repeat. Our DNA is made up of building blocks called “nucleotides.” The CAG trinucleotide repeat happens when too many cytosine, adenine, and guanine nucleotides occur in a row.

The affected DNA gene codes for the androgen receptor (AR), a protein involved in the processing of male hormones. When the gene has extra nucleotides in the form of a CAG trinucleotide repeat, the androgen receptors it codes for are defective. They can’t efficiently transport androgens. This results in some motor neurons being unable to work.

What are the treatments for kennedy-stefanis disease?

There’s currently no cure for spinal and bulbar muscular atrophy, and no medications have been proven to slow or reverse disease progression. However, treatments exist to manage symptoms and reduce their severity.

It’s important to understand that SBMA is a progressive disease. That is, it will continue to worsen over time. Most people with SBMA will eventually need live-in caregivers.

Physical therapy and lifestyle adjustments

In many cases, certain adjustments in your daily life can make managing SBMA a little easier.

Because swallowing can become more difficult, cutting food into smaller pieces can help prevent choking. Consulting with a dysphagia specialist or speech-language pathologist (SLP) can help you practice safe and effective ways to swallow.

Swallowing problems are often factors in early mortality among people with SBMA, due to complications such as pneumonia or asphyxiation. If breathing becomes difficult, respiratory therapy may be helpful. In addition, ventilation aids, such as a bi-level positive air pressure device, can make breathing a little easier.

Because the leg muscles can become weak over time, a cane or walker may be necessary to walk safely and avoid fall-related injuries. Eventually a mobility aid (such as a scooter or wheelchair) may be essential. Physical therapy may help prolong the time before a person with SBMA is required to use a walker or wheelchair.

What are the risk factors for kennedy-stefanis disease?

The role of sex in SBMA

The reason SBMA almost exclusively affects people assigned male at birth (often those with XY chromosomes) is that androgen function is involved in the disease. The androgen testosterone is the dominant male hormone.

In rare cases of people assigned female at birth (often those with XX chromosomes) who have SBMA, symptoms are usually mild. Many don’t have high enough testosterone levels to activate SBMA’s androgen receptor mutation.

People assigned female at birth can be asymptomatic carriers of the disease, and have a 50 percent chance of passing it to their offspring. If a male child (XY chromosomes) gets the gene, they would develop active SBMA. If a female child (XX chromosomes) gets the gene, they would be a carrier.

SBMA research limitations

There isn’t much SBMA research incorporating people with trans, nonbinary, or other gender identities as participants.

However, some interesting findings include:

  • One 2016 study of SBMA in a trans woman found that longterm estrogen therapy (which lowers testosterone and other androgen levels) wasn’t successful in preventing the disease.
  • A 2018 study explains that people assigned female at birth, or those with XX chromosomes, may manifest the disease if carrying the gene and exposed to high testosterone levels.

Is there a cure/medications for kennedy-stefanis disease?

Here’s some important findings on SBMA management:

  • Studies of anti-androgen drugs to block the impact of the AR gene have produced mixed results. There’s not enough research yet to support using these drugs to treat the disease.
  • According to the Muscular Dystrophy Association, a new class of drugs, called selective androgen receptor modulators (SARMs), is being explored. Experts hope these drugs may one day be able to prevent or lessen the severity of SBMA.
  • Testosterone treatment, commonly used to treat gynecomastia and erectile dysfunction (two SBMA symptoms), can actually worsen disease. For those with SBMA experiencing gynecomastia, breast reduction surgery is another option.
  • A small 2013 study of the drug clenbuterol appeared to improve stamina levels in people with SBMA. Clenbuterol has steroid-like properties and is used primarily to help people with breathing difficulties, such as asthma.

Medications to treat tremors and muscle cramps are often prescribed to treat symptoms. These may lessen pain and discomfort, but don’t affect the course of SBMA.

Spinal and bulbar muscular atrophy is a rare genetic disorder that affects certain nerves that control voluntary movement. Caused by an X chromosome defect, it almost always affects people assigned male at birth (those with XY chromosomes). The disease’s genetic cause can be identified in blood tests.

Over time, SBMA can make swallowing and speaking difficult, as well as affect mobility and muscle control. Eventually, people with SBMA will require long-term care to help them with daily activities, including eating and getting dressed.

Medications can treat pain or muscle spasms, but won’t slow the disease. Physical therapy may prolong mobility, assist in safe swallowing, and help those with SBMA hold onto speech capabilities longer.

Unlike ALS — which causes similar symptoms — SBMA progresses slowly and often allows for an average lifespan.

Talk with your doctor about risk factors for you and your family, and any symptoms you may be experiencing.

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