What is MJD?
Machado Joseph Disease | MJD and Arnhem Land
Machado Joseph Disease
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Machado Joseph Disease (MJD) is an hereditary neuro degenerative condition. It is in a ‘family’ of neurodegenerative diseases that includes Huntington’s Disease.
MJD occurs because of a fault in a chromosome that results in the production of an abnormal protein. This protein causes nerve cells to die prematurely in a part of the brain called the cerebellum. The damage to the cerebellum initially causes muscular weakness and progresses over time to a total lack of voluntary control and very significant permanent physical disability.
MJD is an inherited, autosomal dominant disorder, meaning that each child of a person who carries the defective gene has a 50% chance of developing the disease. In addition the mutation is typically expanded when it is passed to the next generation (known as an ‘anticipation effect) this means that symptoms of the disease appear around 8-10 years earlier and are more severe.
There is no known cure for MJD. Progression to dependence occurs over 5 to 10 years and most people are wheelchair bound and fully dependent for activities of daily living within 10-15 years of the first symptoms emerging.
MJD, Arnhem Land and beyond
Previously known as “Groote Eylandt Syndrome”, the effects of MJD have been known to the Aboriginal people of this region for at least four generations.
Following the discovery of the gene for MJD, “Groote Eylandt Syndrome” was confirmed as MJD in 1995 and there are people living with the disease on Groote Eylandt (Angurugu and Umbakumba), Bickerton Island (Milyakburra), Yirrkala, Elcho Island (Galiwin'ku), Darwin, Ngukurr, Birany Birany, Numbulwar, Papunya (near Alice Springs) and Oenpelli.
Spread of the disease to Arnhem Land has been attributed to the 16th Century trading and exploration activities of Portuguese Sailors. Entry into the Australian population is thought to have been through trading relationships between the Aboriginal people of Arnhem Land and the Macassan people of Indonesia, who in turn traded with the Portuguese. However further research and genetic analysis is being undertaken to definitively confirm this.
Although it is impossible to predict the number of people who will develop MJD there are currently around 400 people thought to be “at risk” of developing the disease across the top end.
(At risk individuals are direct descendents of those with the disease).