Cerebral toxoplasmosis in an MS patient receiving Fingolimod

Multiple Sclerosis (MS) is an autoimmune disease in which lymphocytes target putative myelin antigens in the CNS, causing inflammation and neurodegeneration. Fingolimod (FTY720) is an immunosuppressive drug used as a second line therapy for relapsing forms of MS due to its safety profile and good response to treatment. Despite its safety, there are still concerns about the possibility of Fingolimod being linked to the development of opportunistic infections like disseminated varicella zoster infections and herpes simplex encephalitis. In this case report, we describe one patient with past medical history of MS in current treatment with Fingolimod for the last year which presents herself with hemiparesis, fever and fatigue. The initial MRI showed multiple demyelinating-like lesions that could have corresponded to the tumefactive form of MS relapse. The blood work up revealed leukopenia with lymphopenia and a CD4+ count of 200 cell/mm³. Treatment for acute relapse was initiated with little to no response. Further examination was carried by the clinicians, a lumbar puncture was performed and it showed pleocytosis with increased protein levels. Later, several serologic studies were performed and both IgM and IgG antibodies for Toxoplasma were positive. Diagnosis of cerebral toxoplasmosis was made and there was no evidence of HIV infection or other causes of secondary immunodeficiency in this patient, except the use of fingolimod. Evidence of decreased levels of CD4+ due to Fingolimod use is concerning. The risk of opportunistic infections in these patients must be considered in order to start or continue therapy with these agents. Further studies are needed to determine the percentage of the population at risk of immunosuppression and its long-term consequences as well as new actions to prevent infections.