Familial ALS with SOD1 mutation misdiagnosed with polyradiculopathy and myopathy.

We report a 54-year-old male with progressive and asymmetrical lower extremity weakness caused by familial amyotrophic lateral sclerosis (FALS) with a Cu/Zn superoxidase dismutase 1 (SOD1) gene mutation. He was initially misdiagnosed with a lumbosacral polyradiculopathy because of spinal stenosis and underwent a laminectomy surgery with no benefit. He was also misdiagnosed with a myopathy due to moderate CK elevation from acute denervation and pseudomyopathic changes on muscle biopsies from chronic denervation. He eventually developed respiratory muscle weakness and upper motor neuron signs, consistent with familial ALS.