Ocrelizumab-Induced B-Cell Depletion in a Newborn

Ocrelizumab (OCR) is an IgG1 humanized monoclonal antibody directed against CD20. Due to its B-cell-depleting ability, it is used in the treatment of multiple sclerosis, a disease that affects women of childbearing age. Although OCR use is not recommended in pregnancy, in utero exposure has occurred and resulted in normal to absent B cells at birth. Although this has been reported, longitudinal follow-up to determine whether B-cell reconstitution and function remain intact is lacking. Here, we present longitudinal follow-up of a neonate in which in utero OCR exposure resulted in B-cell depletion at birth. B-cell reconstitution occurred at age 4 months, with normal production of immunoglobulins and responses to vaccines noted at age 1 year. Awareness among pediatricians and neurologists regarding the effects of anti-CD20 therapies on the developing fetus and neonate may be lacking. An absence of B cells at birth should raise concern and be followed closely, as humoral immunity is an essential mechanism of passive and active immunity against infection throughout the lifetime. Recognition of patients exposed to anti-CD20 therapies during pregnancy allows for early detection and referral to an immunologist.