Possible lansoprazole-induced eosinophilic syndrome

OBJECTIVE: To report a case of myalgia with eosinophilia related to lansoprazole administration. CASE SUMMARY: A 50-year-old white woman developed severe myalgia 1 week after starting lansoprazole. During the treatment course, the patient was also found to have eosinophilia. The myalgia and eosinophilia resolved 40 days after lansoprazole was stopped and 18 days after prednisone therapy was begun. The patient was not rechallenged with lansoprazole. DISCUSSION: To our knowledge, this is the first reported case of lansoprazole-induced eosinophilic syndrome. Clinically, it is difficult to distinguish between eosinophilia-myalgia syndrome and eosinophilic fasciitis, which are probably part of a continuum of eosinophilic disorders. This patient presented with symptoms of both syndromes. Although other causes cannot be completely ruled out, the time course strongly suggests that lansoprazole was the causative agent. CONCLUSIONS: It is important to consider medications when diagnosing patients with hypereosinophilia and/or myalgia.