Acute respiratory failure due to diaphragmatic weakness revealing a polymyositis.

Of the different respiratory disorders that complicate the course of polymyositis, diaphragmatic weakness is one that is seldom described and most often suspected rather than confirmed. We report a case of severe diaphragmatic weakness as a cause of acute respiratory failure revealing a polymyositis. The diaphragmatic involvement was proven by a very low esophageal pressure in response to cervical magnetic stimulation of the phrenic nerve. Corticosteroids and intravenous gammaglobulin, combined with mechanical ventilation, achieved a progressive recovery of diaphragmatic weakness.