Machado-Joseph disease (MJD), which is also called spinocerebellar ataxia type 3, is a rare hereditary ataxia (ataxia is a medical term meaning lack of muscle control).
The disease is caused by a mutation in the ATXN3 gene, which is located on chromosome 14q.
Symptoms can begin any time between early adolescence and about 70 years of age. MJD is an autosomal dominant disease, meaning that if either parent gives the defective gene to a child, the child will show symptoms of the disease.
The disease is characterized by:
- Slowly progressive clumsiness and weakness in the arms and legs
- A staggering lurching gait easily mistaken for drunkenness
- Difficulty with speech and swallowing
- Involuntary eye movements
- Double vision
- Frequent urination
Some individuals also have dystonia (sustained muscle contractions that cause twisting of the body and limbs, repetitive movements, abnormal postures, and rigidity) or symptoms similar to those of Parkinson’s disease. Others have twitching of the face or tongue, or peculiar bulging eyes. Almost all individuals with MJD experience vision problems, including double vision or blurred vision, loss of the ability to distinguish color and/or contrast, and inability to control eye movements.
The severity of the disease is related to the age of onset, with earlier onset associated with more severe forms of the disease. MJD is a progressive disease, meaning that symptoms get worse with time. Life expectancy ranges from the mid-thirties for those with severe forms of MJD to a normal life expectancy for those with mild forms. The cause of death for those who die early is often aspiration pneumonia.
MJD is incurable, but some symptoms of the disease can be treated. For those individuals who show parkinsonian features, levodopa therapy can help for many years. Treatment with antispasmodic drugs, such as baclofen, can help reduce spasticity. Botulinum toxin can also treat severe spasticity as well as some symptoms of dystonia. Speech problems and trouble swallowing can be treated with medication and speech therapy. Physiotherapy can help patients cope with disability associated with gait problems. Physical aids, such as walkers and wheelchairs, can assist with everyday activities.