Interferons are a set of cytokines that activate antiviral responses by the body's immune cells and have been a mainstay of treatment of hepatitis C. Well-known neuropsychiatric effects of interferons include depression, irritability, and impaired concentration. A condition reported rarely in association with this treatment is parkinsonism. We report 2 patients who developed parkinsonism in conjunction with treatment of hepatitis C with alpha interferons. The first is a 51-year-old man who developed intermittent rest and postural tremor during treatment with pegylated interferon alpha ribavirin, and amantadine, with resolution of the symptoms after completing a 36-week course. Similar tremor recurred 3 years later with progressive parkinsonism, compatible with Parkinson disease (PD). The second patient is a 71-year-old man who developed postural tremor 8 weeks into a regimen of consensus interferon. Tremor resolved at completion of 48 weeks of interferon. Pegylated interferon alpha and ribavirin were started 2 years later because of lack of sustained virologic response. At 24 weeks of treatment, postural tremor returned along with features and a progressive course compatible with PD. Thus, both patients presented here developed (rest and/or postural) tremor during interferon therapy followed by delayed onset of parkinsonism. We identified 10 other cases in the literature of parkinsonism/PD associated with interferon administration. This report reviews the clinical presentation and potential pathophysiological mechanisms and recommends that physicians who prescribe interferon be vigilant for symptoms of PD in their patients.
*Division of Gastroenterology, Department of Medicine, University of Pennsylvania, Philadelphia, PA; and †Department of Medicine, University of Vermont College of Medicine; and ‡Department of Neurological Sciences, Binter Center for Parkinson's Disease and Movement Disorders, University of Vermont Medical Center, Burlington, VT.
Address correspondence and reprint requests to James T. Boyd, MD, Department of Neurological Sciences, Binter Center for Parkinson's Disease and Movement Disorders, University of Vermont Medical Center, 1 South Prospect St, Burlington, VT 05401; E-mail: firstname.lastname@example.org
Conflicts of Interest and Source of Funding: K.J.W., R.W.H., and J.T.B. have no financial disclosures or conflicts of interests related to the content of this manuscript. E.L.W. has previously served on the DSMB for Roche and AbbVie and has previously served as a clinical trials site investigator for Merck (formerly Schering Plough), Roche, and Amgen.