Abstract
Guillain-Barré syndrome (GBS) and polymyositis (PM) are two rare autoimmune diseases, one of which affects the peripheral nervous system and other the muscle. We report the case of a young woman with no previous medical history who was hospitalized with an ascending paralysis associated with acute respiratory failure due to a GBS. The patient was treated with plasmapheresis with unfavorable outcome and permanent proximal muscular disability. The diagnosis of an associated PM was retained based on biological myolysis and the results of electromyography and muscular biopsy. To our knowledge, this association of GBS and PM has been reported only once in the literature. The search for syndromic associations in the presence of an autoimmune helps to avoid diagnostic errors.