We aim to report a rare complication of ocrelizumab.

Ocrelizumab is a humanized anti-CD20 monoclonal antibody and highly effective disease-modifying therapy for multiple sclerosis(MS). Clinical trials and observational studies showed that B-cell-depleting agents can cause hypogammaglobulinemia, increasing the risk of infections, including viruses. We describe a patient with relapsing-remitting MS on Ocrelizumab who developed severe enterovirus radiculomyelitis.

A retrospective chart review of an MS patient on Ocrelizumab with enterovirus radiculomyelitis.

A 31-year-old man with a history of MS without evidence of disease activity on Ocrelizumab presented with fever, headache, nausea, vomiting, urinary retention, and back pain, followed by bilateral leg weakness after 3 days. He was found to have decreased strength in the lower extremities and areflexia at the knees and ankles bilaterally. An MRI showed new, diffuse T2 hyperintensity throughout the spinal cord from C1 to conus with enhancement of the lumbar nerve roots. He had B-cell depletion and lower IgG levels than his baseline. A nasal swap was positive for Enterovirus. CSF studies showed lymphocytic pleocytosis and elevated protein. Enterovirus PCR in the CSF was positive. He was treated with a 5-day course of IVIG, high-dose steroids, and Fluoxetine 20 mg daily. His symptoms steadily improved, and after a week, he was able to ambulate independently. Repeat LP after a month was negative for Enterovirus.

Ocrelizumab can lead to lower IgG levels, increasing susceptibility to viral diseases, including enterovirus, as reported in Rituximab-related hypogammaglobulinemia and X-linked agammaglobulinemia, suggesting that the underlying pathology might be related to the lack of neutralizing viral antibodies. To our knowledge, this is the first Ocrelizumab-associated severe enterovirus radiculomyelitis case. In addition to IVIG and steroids, the patient was treated with fluoxetine, that inhibits enterovirus replication in vitro. Our study highlights vigilance for rare viral infections while using Ocrelizumab, especially in patients with hypoglobulinemia.