MDA leads the search for treatments and therapies for spinal-bulbar muscular atrophy (SBMA). The Association also provides comprehensive supports and expert clinical care for those living with SBMA.
In this section, you’ll find up-to-date information about spinal-bulbar muscular atrophy, as well as many helpful resources. This information has been compiled with input from researchers, physicians and people affected by the disease.
As you learn more about SBMA, always remember that you’re not alone. MDA is here for you and your family, standing ready to provide help and hope. There is a place for you in the MDA SBMA community.
MDA provides support by:
Once you sign up with your local MDA office , you’ll begin receiving MDA’s quarterly Quest  magazine, where you’ll find news about research and health care, helpful products and devices, social and family issues, and more.
In addition, MDA will keep you informed through e-alerts, educational publications and speakers, seminars, videos and newsletters.
Please know that there’s a role for you in the fight against spinal-bulbar muscular atrophy The MDA community is strong and dedicated, with opportunities for involvement at all levels, such as:
Please know that there’s an important role for every member of the SBMA community. We urge you to contact your local MDA office  to learn more.
A SBMA diagnosis doesn’t mean an end to your hopes and dreams. Changes, challenges and adaptations lay ahead, but also opportunity, fulfillment, joy and hope for a future free of spinal-bulbar muscular atrophy.
Never forget that MDA is here to help.
Spinal-bulbar muscular atrophy (SBMA) is a genetic disorder in which loss of motor neurons — nerve cells in the spinal cord and brainstem — affects the part of the nervous system that controls voluntary muscle movement.
SBMA is sometimes called Kennedy disease, after William Kennedy, the physician who originally described it in 1968. It's also sometimes called bulbospinal muscular atrophy. The adjective bulbar refers to a bulblike structure in the lower part of the brain that contains nerve cells controlling muscles in the face, mouth and throat.
SBMA causes weakness of the facial and swallowing muscles, as well as limb weakness and some hormonal abnormalities. For more, see Signs and Symptoms .
SBMA is caused by a genetic defect on the X chromosome. It usually affects only men, although female carriers may have a mild form of the disease. Onset is typically in adulthood, between ages 30 and 50. For more, see Causes/Inheritance .
SBMA progresses very slowly, over decades.
SBMA research  has focused largely on strategies to block the formation of abnormal clumps inside cells; ways to interfere with some of the actions of male hormones; and methods to influence how genetic instructions are "read" by cells.
Spinal-bulbar muscular atrophy (SBMA) mostly affects men and usually begins between the ages of 30 and 50, although symptoms have begun in boys as young as 15 or men as old as 60. In those few women who have the disease, the symptoms are usually mild.
The bulbar muscle involvement in SBMA can be significant, affecting speech, chewing and swallowing. The swallowing muscle weakness can lead to choking on food or liquids or inhaling them into the lungs. This kind of inhalation can lead to obstruction of airways or infection. Weakness in the throat muscles also can make breathing during sleep  difficult.
Facial muscle weakness can occur, making it hard to smile or convey emotion through facial expressions.
SBMA also involves weakness and atrophy of the arm and leg muscles, particularly those nearest the center of the body. Twitching or cramping of muscles can occur.
Weakness of the limb muscles is often first noticed as trouble with stairs or difficulty walking long distances, such as through malls or parking lots.
In addition, men with SBMA can develop enlarged breasts (gynecomastia), and may have reduced fertility and atrophy (shrinkage) of the testicles. These symptoms, which are important clues to the cause of the disease, are related to abnormal processing of male hormones, known as androgens.
Female carriers of the flawed gene that causes SBMA  can develop muscle cramps and twitches, particularly as they get into their 60s or 70s.
Although women also produce and use androgens, they do so at lower levels than men and hormonal differences between the sexes are thought to contribute to SBMA's milder course in women.
The age distribution and symptoms of spinal-bulbar muscular atrophy (SBMA) overlap with those of another motor neuron disease, amyotrophic lateral sclerosis (ALS) , so the two are sometimes confused early in the diagnostic work-up. It’s worth knowing which disorder affects you or your family member, since ALS is a much more profound and rapidly progressing condition than SBMA.
The first steps in diagnosis of a neuromuscular disease are usually an in-office physical examination and family history, with some nonpainful tests to distinguish SBMA from similar conditions.
The doctor may order a simple blood test for an enzyme called creatine kinase (CK) . This enzyme leaks out of muscles that are deteriorating. Although it’s a nonspecific test (since CK levels are elevated in many neuromuscular diseases), it’s often useful anyway. High blood CK levels aren’t harmful; they’re just an indicator of muscle damage.
The doctor probably will recommend genetic testing if SBMA is suspected. Requiring only a blood sample, genetic testing is the most accurate way to diagnose the condition. For more on getting a definitive genetic diagnosis, see The Genie's Out of the Bottle: Genetic testing in the 21st century .
Other tests  that may be requested are those that measure nerve conduction velocity — the speed with which signals travel along nerves — and the electrical activity in muscle. The latter is called an electromyogram, or EMG. Nerve conduction velocity tests involve sensations that feel like mild electric shocks, and EMGs require that short needles be inserted in the muscles.
An SBMA diagnosis has implications for the whole family  that must be considered. It’s a good idea to talk with a genetic counselor when someone in the family is found to have a genetic disease  or when testing is undertaken. Your MDA clinic  can help you find one.
The genetic flaw in X-chromosome spinal-bulbar muscular atrophy (SBMA) is an expanded section of DNA — called a trinucleotide repeat — in a gene that carries instructions for a protein known as the androgen receptor.
The normal function of the androgen receptor is to help cells process androgens (male hormones). When the androgen receptor has extra DNA, it’s longer than it’s supposed to be and may be sticky. The flawed androgen receptor can’t transport male hormones in the right way, and it may "gum up the works" of motor neurons in other ways that keep them from performing their usual functions.
The gene flaw that causes SBMA is on the X chromosome, leading to an X-linked inheritance pattern.
Females have two X chromosomes, and males have an X and a Y chromosome. Females who have a gene flaw on one X chromosome are usually considered carriers of an X-linked disease (although sometimes they can have a mild form of the disease). Males, in contrast, have no second X to protect them and typically show the full effects of the flaw on their single X chromosome.
Each son of a woman who carries an X-linked disease has a 50 percent chance of inheriting the gene flaw and developing the disease. Each daughter has a 50 percent chance of inheriting the gene flaw and being a carrier herself.
Genetic testing via a blood test is available to help diagnose SBMA  and to detect SBMA carriers. For more information on genetics and genetic testing, see the MDA publication Facts About Genetics and Neuromuscular Diseases .
|Noninvasive ventilation can be delivered through a mask or mouthpiece. Photo courtesy of Respironics.|
In spinal-bulbar muscular atrophy, swallowing and chewing muscle weakness pose a choking  hazard.
A swallowing specialist should be consulted to determine the safest ways of swallowing, and to learn ways to alter food consistency. A feeding tube  can be considered in cases of extreme weakness.
Weakness in the throat muscles also can make breathing during sleep  difficult. Noninvasive ventilation aids  such as a bilevel positive air pressure device (such as BiPAP by Respironics), which pushes in air under pressure, can help with this.
As the disease progresses over many years, a scooter or wheelchair may eventually be needed for longer distances.
MDA researchers first identified the genetic defect underlying spinal-bulbar muscular atrophy (SBMA) in the early 1990s. Since then, many MDA-supported research groups have worked to understand the disease and develop treatments for it.
Many MDA-supported projects are focused on understanding how the downstream effects of mutations in the androgen receptor gene  affect cells, and developing methods to overcome or compensate for these effects.
Recently, some MDA researchers have been looking into the possibility of using a new class of drugs called selective androgen receptor modulators (SARMs) to treat SBMA.
A clinical trial is a test in humans of an experimental medication or therapy. Clinical trials are experiments, not treatments, and participation requires careful consideration.
Although it's possible to benefit from participating in a clinical trial, it's also possible that no benefit — or even harm — may occur. Keep your MDA clinic  doctor informed about any clinical trial participation. (Note that MDA has no ability to influence who is chosen to participate in a clinical trial.)
For more about clinical trials in general, see Learn About Clinical Studies , and to learn more about trial participation in neuromuscular disease, read the Quest magazine article Being a Co-Adventurer .
For a more refined list of SBMA clinical trials, visit ClinicalTrials.gov , a registry of federally and privately supported clinical trials in the United States and around the world. Select "Search for Clinical Trials," and follow the instructions to narrow down your search results.