Flail arm syndrome (FAS) is a benign clinical variant of amyotrophic lateral sclerosis (ALS). It occurs predominantly in males and has a slow onset and a long survival. The major clinical features of FAS are significant muscle weakness and amyotrophia in the proximal segments of both upper limbs and mild involvement of both lower limbs and bulbar muscles. Nerve electrophysiological examination shows extensive neurogenic damage in more than three segments of the spinal cord. At present, there are no drugs for FAS, and riluzole is the only drug approved for the treatment of ALS.