MJD can be diagnosed by recognizing the symptoms of the disease and by taking a family history. Physicians ask patients questions about the kind of symptoms relatives with the disease had, the progression and harshness of symptoms, and the ages of onset in family members. Presymptomatic diagnosis of MJD can be made with a genetic test. The direct detection of the genetic mutation responsible for MJD has been available since 1995. Genetic testing looks at the number of CAG repeats within the coding region of the MJD/ATXN3 gene on chromosome 14. The test will show positive for MJD if this region contains 61-87 repeats, as opposed to the 12-44 repeats found in healthy individuals. A limitation to this test is that if the number of CAG repeats in an individual being tested falls between the healthy and pathogenic ranges (45-60 repeats), then the test cannot predict whether an individual will have MJD symptoms. Classification There are five sub-types of MJD that are characterized by the age of onset and range of symptoms. The sub-types illustrate a wide variety of symptoms that patients can experience. However, assigning individuals to a specific sub-type of the disease is of limited clinical significance. * Type I affects approximately 13% of individuals with MJD and has onset of symptoms between the ages of 10 and 30 years old. It usually progresses quickly, with patients experiencing severe rigidity and dystonia. * Type II is the most common sub-type, affecting approximately 57% of individuals with MJD and symptoms typically begin between 20 and 50 years of age. It has an intermediate rate of progression and causes symptoms that include ataxia and spasticity, along with other upper motor neuron signs such as exaggerated deep tendon reflexes (DTRs). * Type III occurs in approximately 30% of MJD patients and has a relatively slow progression, with symptoms typically arising between the ages of 40 and 70. Symptoms include muscle twitching and cramps, unpleasant sensations such as numbness, tingling, and pain in the feet and hands, and limb muscle atrophy. Nearly all patients experience a decline in their vision experienced as blurred vision, double vision, inability to control eye movements, and/or loss of capability to distinguish color. Some patients also experience Parkinsonian symptoms. * Type IV is distinguished by Parkinsonian symptoms that respond particularly well to levodopa treatment. * Type V appears to resemble Hereditary Spastic Paraplegia; however, more research is needed to conclude the relationship between Type V MJD and hereditary spastic paraplegia.
Machado–Joseph disease
Darier's disease
Caroli disease
Borna disease
Lev's disease
Tornwaldt's disease
Marchiafava–Bignami disease
Bright's disease