A case of exacerbated multiphasic disseminated encephalomyelitis after interferon β treatment.

Acute disseminated encephalomyelitis (ADEM) is an inflammatory demyelinating disorder of the central nervous system (CNS), which can be monophasic or with repeated episodes. Relapsing ADEM can be misdiagnosed as multiple sclerosis (MS). We describe here a 16-year-old female patient with multiphasic disseminated encephalomyelitis (MDEM), which was exacerbated after an interferon beta (INF-β) treatment. The patient presented with polysymptomatic and encephalopathic features at the first attack and was definitively diagnosed with ADEM. During the following 28months, she had two relapses, with the lesions spatially disseminated in time and space, but without encephalopathy. She was diagnosed with MS and started on treatment with IFN-β injection. A severe relapse occurred 5months after starting IFN-β treatment, with both the clinical and MRI characteristics worse than during the former 2 relapses, meeting the diagnostic criteria for MDEM. Treatment with IFN-β was halted, with no new relapses observed over the following 9months. These findings suggest that treating MDEM patients with IFN-β may exacerbate the disease, similar to that observed during IFN-β treatment of patients with neuromyelitis optica. Caution should be exercised when treating these patients with IFN-β.