60  old man presented with 5 year history of progressive proximal lower limb weakness as manifested by difficulty raising from a chair and climbing stairs. Since about 2 years before, he developed abnormal gait, arm weakness, exertional shortness of breath, and orthopnea. He also had severe difficulty turning in or getting up from the bed. There was also long history of intermittent horizontal diplopia, but no ptosis, dysphagia, pain, sensory and sphincter symptoms. Exam showed normal cranial nerves except for partial paresis of the abduction of the left eye. He had mild deltoid weakness but other proximal and distal muscles of the upper limbs had normal strength. There was also 4/5 weakness of hip flexion, abduction and adduction, and normal strength of distal lower limb muscles. The neck extension was 4/5 in strength, he developed stooped posture (bent spine) after taking a few steps and had waddling gait. No fasciculations were noted, and sensory exam and deep tendon reflexes were normal.

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