MJD is characterized by slowly progressive clumsiness in the arms and legs, a staggering lurching gait that can be mistaken for drunkenness, difficulty with speech and swallowing, impaired eye movements sometimes accompanied by double vision or bulging eyes, and lower limb spasticity. Some individuals develop dystonia (sustained muscle contractions that cause twisting of the body and limbs, repetitive movements, and abnormal postures) or symptoms similar to those of Parkinson’s disease. Others may develop fasciculations (twitching) of the face or tongue, neuropathy, or problems with urination and the autonomic nervous system.
The clinical manifestations of MJD can be highly variable, even among affected persons in the same family. This wide range in symptoms reflects the particular type of mutation that causes MJD: a repeat expansion in the DNA code that varies in size among affected persons. The longer the expansion, typically the more severe the disease. In other words, longer repeat expansions tend to cause disease that begins earlier in life and shows a broader range of neurological symptoms. In most individuals with MJD, symptoms typically begin in the third to fifth decade of life but can start as early as young childhood or as late as 70 years of age.
MJD is a progressive disease, meaning that symptoms worsen with time. Life expectancy ranges from the mid-30s for those with the most severe forms of early onset MJD to a nearly normal life expectancy for those with mild, late onset forms. The cause of death for those who die early from the disease is often aspiration pneumonia.
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