A 45 year-old man went to the emergency room due to disease duration of 15 days of insidious onset and progressive course. It began with symmetrical weakness and pain in feet and ankles that extends upward to the knees. Later, this progressed to paraparesis with Creatine phosphokinase levels of 44,270 U/L and respiratory failure that required mechanical ventilation. Electromyography and muscle biopsy of quadriceps were made. The patient responded to corticotherapy in pulses and supporting management. The presentation of ascending paresis suggested the diagnosis of Guillain-Barré syndrome. However, the degree of muscle involvement with rhabdomyolysis explains the neurological damage by itself. The biopsy revealed pathological criteria for necrotizing autoimmune miopathy (NAM), as well as other clinical and laboratory evidence. Patient disease continued and reached criteria for systemic lupus erythematosus (SLE). To our best knowledge, this is the first report of the NAM and SLE association. © 2012 Elsevier España, S.L.