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Primary lateral sclerosis (PLS) is a rare neuromuscular disease characterized by progressive muscle weakness in the voluntary muscles. PLS belongs to a group of disorders known as motor neuron diseases. Motor neuron diseases develop when the nerve cells that control voluntary muscle movement degenerate and die, causing weakness in the muscles they control. PLS only affects upper motor neurons.〔(【引用サイトリンク】title=Motor neuron diseases )〕 There is no evidence of the degeneration of spinal motor neurons or muscle wasting (amyotrophy) that occurs in amyotrophic lateral sclerosis (ALS). ==Symptoms and progression== Onset of PLS usually occurs spontaneously after age 50 and progresses gradually over a number of years, or even decades. The disorder usually begins in the legs, but it may start in the tongue or the hands. Symptoms may include difficulty with balance, weakness and stiffness in the legs, and clumsiness. Other common symptoms are spasticity (involuntary muscle contraction due to the stretching of muscle. Muscle contraction is dependent on the velocity of the stretch) in the hands, feet, or legs, foot dragging, and speech and swallowing problems due to involvement of the facial muscles. Breathing may also become compromised in the later stages of the disease, causing those patients who develop ventilatory failure to require noninvasive ventilatory support.〔(【引用サイトリンク】 Primary Lateral Sclerosis )〕 Hyperreflexia is another key feature of PLS as seen in patients presenting with the Babinski's sign. Some people present with emotional lability and bladder urgency,〔 and occasionally people with PLS experience mild cognitive changes detectable on neuropsychological testing, particularly on measures of executive function. PLS is not considered hereditary when onset is in adulthood; however, juvenile primary lateral sclerosis (JPLS) has been linked to a mutation in the ALS2 gene which encodes the cell-signalling protein alsin. The issue of whether PLS exists as a different entity from ALS is not clear, as some patients initially diagnosed as having PLS ultimately develop lower motor neuron signs. There are no specific tests for the diagnosis of PLS. Therefore, the diagnosis occurs as the result of eliminating other possible causes of the symptoms and by an extended observation period. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「primary lateral sclerosis」の詳細全文を読む スポンサード リンク
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