Study design: Single-subject case (a quadriplegic female, 56 years).
Objectives: To describe a new case of eosinophilic pleural effusion induced by dantrolene chronic administration.
Setting: Physical medicine and rehabilitation unit in a teaching hospital, France.
Methods: Diagnosis of an eosinophilic pleural effusion induced by dantrolene without any respiratory symptoms, except a decrease of breath sounds on the right lung base.
Results: Chest radiograph revealed a right-sided pleural effusion, and blood cell count a significant peripheral eosinophilia. Thoracenthesis contained 85% of eosinophils. The other explorations eliminated other causes of pleural effusion. The diagnosis of drug-induced effusion was almost sure and led us to discontinue the dantrolene. After 3 months, she had completely recovered. These characteristics, similar to the eight other cases described in the literature, are essential for the diagnosis of pleural effusion induced by dantrolene.
Conclusion: Dantrolene, a long-acting skeletal muscle relaxant, is well known to induce liver side effects but it can also induce pleural pericarditis. The pathogenesis is still not clearly identified, but similarities of chemical structures of dantrolene and nitrofurantoine make us think that it could be the same mechanism. The association between dantrolene and nitrofurantoine may have contributed to the expression of the pleural effusion.