CausesBy Mayo Clinic staff
In primary lateral sclerosis (PLS), nerve cells in the brain that control movement fail over time. This loss causes movement problems, such as slow movements, balance problems and clumsiness.
Adult primary lateral sclerosis
The cause of adult primary lateral sclerosis is unknown. In most cases, it's not an inherited disease, and it's not known why or how it begins.
Juvenile primary lateral sclerosis
Juvenile primary lateral sclerosis is caused by mutations in a gene called ALS2.
Although researchers don't understand how this gene causes the disease, they know that the ALS2 gene is responsible for giving instructions for creating a protein called alsin, which is present in motor neuron cells.
When the instructions are changed in someone with juvenile PLS, the protein alsin becomes unstable and doesn't work properly, which in turn impairs normal muscle function. Adults who get primary lateral sclerosis don't appear to have the same gene mutation.
Juvenile primary lateral sclerosis is an autosomal recessive disease, meaning that both parents have to be carriers of the gene to pass it to their child, even though they don't have the disease themselves.
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