[3] Some symptoms, such as clumsiness and rigidity, make MJD commonly mistaken for drunkenness or Parkinson's disease.

Symptoms of MJD are memory deficits,[4] spasticity, difficulty with speech and swallowing, weakness in arms and legs, clumsiness, frequent urination and involuntary eye movements.

[6] Spinocerebellar ataxia type 3 (SCA3) on the Azores are believed to have come from Portugal's northeast where Sephardic Jews lived.

In exon 10 the gene contains lengthy irregular CAG repeats, producing a mutated protein called ataxin-3.

These insoluble aggregates are hypothesized to interfere with the normal activity of the nucleus and induce the cell to degenerate and die.

[citation needed] MJD can be diagnosed by recognizing the symptoms of the disease and by taking a family history.

[3] Physiotherapy/Physical Therapy and/or occupational therapy can help patients by prescribing mobility aids to increase the patients' independence, providing gait training, and prescribing exercises to maintain the mobility of various joints and general health to decrease the likelihood of falls or injuries as a result of falls.

It is named after two men ("William Machado" and "Antone Joseph") who were the patriarchs of the families in which the condition was initially described.

[22] Brazilian comedian, actor and TV personality Guilherme Karam was diagnosed with Machado–Joseph disease, having inherited it from his mother, like his brother and sister.

[24] In a video on Facebook just days after Karam's death, Brazilian personality, journalist and television presenter, Arnaldo Duran publicly acknowledged his condition with Machado-Joseph.

[26] Also, as there currently is no clinical intervention to prevent the onset of the disease symptoms, there is discourse over whether individuals should get tested or not.

[18] The benefits of having MJD testing include a reduction in anxiety and uncertainty, and the ability to plan for the future.

Some disadvantages include the anticipation of negative results and the individual's difficulties in adapting to this outcome.