Malignant Syndrome and Serotonin Syndrome in a General Hospital Setting: Clinical Features, Frequency and Prognosis

Objective The differences in the frequency and clinical features of malignant syndrome (MS) and serotonin syndrome (SS) in same population have only rarely been reported. To report the frequency and clinical features of MS and SS in a general hospital setting. Methods The clinical and laboratory features of patients with MS and those with SS, who were consecutively admitted to Chiba Rosai Hospital, during the past 4.5 years were reviewed. Results Of the 2005 patients admitted, MS was observed in 16 patients (0.8%) and SS in 2 (0.1%). In the 16 patients with MS, the underlying disorder included depression (n = 5), and dementia or parkinsonism (n = 11). The underlying etiology of the 2 patients with SS was depression. In 5 patients, MS was difficult to distinguish from SS because of overlapping symptoms and signs and/or treatments with both neuroleptic and serotoninergic drugs. Of the 16 patients with MS, 1 died, 1 remained wheelchair-bound, 4 were able to walk with assistance, and 10 regained their ability to ambulate independently. The 2 patients with SS recovered after cyproheptadine therapy and were discharged on foot. Conclusion MS occurs more frequently than SS in the general hospital setting. Underlying aetiologies in patients with MS were more common due to dementia or parkinsonism than in patients with psychiatric disorders. The differential diagnosis of MS and SS is often difficult and the diagnostic sensitivities largely differ for each of the diagnostic criteria. As a result, the establishment of new diagnostic criteria that specifically focus on distinguishing MS from SS is therefore required.