Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3, or SCA3, is an inherited ataxia disorder. Ataxia can affect muscle control, resulting in a lack of balance and coordination. Specifically, MJD causes a progressive lack of coordination in the arms and legs. People with the condition tend to have a distinctive walk, similar to a drunken stagger. They may also have difficulty speaking and swallowing.
MJD has been linked to a genetic defect in the ATXN3 gene on chromosome 14. It is an autosomal dominant condition, meaning only one parent has to have the gene for a child to be affected. If you have the condition, your child has a 50 percent chance of inheriting it. The condition is most commonly seen in people of Portuguese or Azorean descent. On the island of Flores in the Azores, 1 in 140 people is affected. However, MJD can occur in any ethnic group.
There are three different types of MJD. Which type you have depends on when symptoms start and the severity of those symptoms. Here is a look at the most common characteristics and symptoms of those three types:
Many individuals with MJD also have vision problems, such as double vision (diplopia) and inability to control eye movements, as well as trembling in their hands and problems with balance and coordination. Others may develop facial twitching or problems urinating.
How MJD Is Diagnosed
MJD is diagnosed based on the symptoms you are experiencing. Since the disorder is inherited, it is important to look into your family history. If relatives have symptoms of MJD, ask when their symptoms began and how quickly they developed. A definitive diagnosis can only come from a genetic test, which would look for defects in your 14th chromosome. For those living with early onset MJD, life expectancy can be as short as the mid-30s. Those with mild MJD or a late-onset type generally have a normal life expectancy.
Currently, there is no cure for Machado-Joseph disease. We also do not have a way to stop its symptoms from progressing. There are, however, medications that can help relieve symptoms. Baclofen (Lioresal) or botulinum toxin (Botox) can help reduce muscle spasms and dystonia. Levodopa therapy, a therapy used for people with Parkinson's disease, can help lessen stiffness and slowness. Physical therapy and assistive equipment can help individuals with movement and daily activities. For visual symptoms, prism glasses can help reduce blurred or double vision.