Machado-Joseph Disease (MJD) is a rare, inherited neurodegenerative disorder that affects muscle control and movement. It is a type of spinocerebellar ataxia (SCA3) and is caused by a genetic mutation that leads to the gradual loss of nerve cells in specific areas of the brain, particularly the cerebellum and brainstem.

Symptoms of MJD

MJD primarily affects movement and coordination, leading to symptoms such as:

• Progressive loss of balance and coordination (ataxia)

• Muscle stiffness or spasticity

• Weakness in limbs

• Difficulty with speech (dysarthria) and swallowing (dysphagia)

• Involuntary eye movements (nystagmus)

• Vision problems, including double vision

• In some cases, Parkinson-like symptoms (tremors, muscle rigidity)

Causes and Inheritance

MJD is genetically inherited in an autosomal dominant pattern, meaning that a child has a 50% chance of inheriting the faulty gene if one parent carries it. The disease is caused by a CAG repeat expansion in the ATXN3 gene. The larger the repeat, the earlier and more severe the onset of symptoms.

Progression and Treatment

MJD is a progressive disease, meaning symptoms worsen over time. The rate of progression varies, but most individuals eventually lose the ability to walk and require mobility aids. There is no cure, but treatments focus on symptom management, including:

• Physiotherapy and occupational therapy to maintain mobility and function

• Speech therapy to assist with communication and swallowing difficulties

• Medications for muscle stiffness, pain, and tremors

Who is Affected?

MJD is found in various populations worldwide, with a higher prevalence in certain regions, including parts of Portugal, Brazil, Japan, and some Indigenous communities in Australia.