Unexpected and persistent depletion of B lymphocytes CD20 following a minimum dose of anti-CD20 antibody (Rituximab)

Rituximab is a chemeric murine/human anti-B lymphocyte antigen CD20 monoclonal antibody used in the treatment of rheumatoid arthritis resistant to treatment by one or more anti TNF-alpha therapies (1). The recommended dose for an efficient depletion of the B CD 20 lymphocytes in rheumatoid arthritis is two infusions of 1000 mg, with the second infusion being administered two weeks after the first. At this dose, one obtains a rapid and persistent depletion of CD 20 cells, with repopulation occurring, on the average, in about eight months (2). Here, we present a case of a woman treated with only 50 mg of rituximab, who underwent both a rapid and pronounced reduction of B CD 20 lymphocytes..