A retrospective real-world cohort study in Mexico linked rituximab treatment to high rates of secondary hypogammaglobulinemia. Among patients treated with rituximab, 42.9% developed secondary hypogammaglobulinemia, highlighting a need for regular immunoglobulin monitoring. The work adds pragmatic data on immunoglobulin suppression outside controlled trial settings, where patient selection and follow-up intensity can differ. For immunology and hematology teams, the signal argues for tighter lab surveillance and proactive infection-risk assessment in rituximab-treated populations. Clinically, the finding is particularly relevant for long-duration or combination regimens where cumulative immune suppression may compound adverse outcomes.