Tumefactive Multiple Sclerosis, A Rare Variant Presenting as Multiple Ring-enhancing Lesions in an Immunocompetent Patient: A Case Report.

Tumefactive multiple sclerosis (TMS) is a rare entity which can be difficult to diagnose unless definitive diagnostic measures are taken. TMS is characterized by solitary or multiple lesions that are sized > 2 cm, with/without mass effect, edema, and ring enhancement on magnetic resonance imaging (MRI). The demyelinating lesion can mimic infections, vascular lesions, and inflammatory lesions. The clinical presentation is highly dependent on the area of the brain which is affected, and this can lead to a variety of signs and symptoms. Herein, we present the case of a 40-year-old immunocompetent female with a history of right-sided numbness of her face, arm, and leg associated with muscle weakness for about a week. Workup included an MRI showing ring-enhancing lesions in the white matter of the brain, zero oligoclonal bands in the CSF, a normal immunoglobulin G (IgG) index, and an elevated myelin basic protein (MBP) in the CSF. A biopsy was obtained that showed predominant macrophage infiltrate with loss of myelin but the preservation of axons. Suspecting a demyelinating pathology, the patient was informed that she would be started on intravenous dexamethasone for an eight-day course. With subsequent completion of this course in the hospital, the patient was discharged on oral prednisone daily for a month and a referral leading to a definitive diagnosis of TMS. The patient was started on interferon beta-1a and subsequently relapsed due to noncompliance. However, further workup showed a reduction in the mass-like lesions and a response to therapy. If suspicion for TMS is high despite workup, steroids can be used with immunomodulators in the interim to combat symptoms and potentially reduce lesions and potentially subvert the need for biopsy.