Rituximab is effective in B-cell lymphomas but also in inflammatory diseases such as rheumatoid arthritis (RA).1 Several cases of late-onset neutropenia (LON) have been described in lymphomas.2^–4 Reversible rituximab-related LON tends to occur 2–6 months after rituximab administration. The post-marketing rate of LON appears very low (<0.02% in a total of 300 000 patients).2 Its mechanism is unknown, although several hypotheses have been suggested.

We report one case of rituximab-related LON for the first time outside the lymphoma field and explore some of the proposed …