Relationship between lymphocyte count and risk of infection in Japanese rheumatoid arthritis patients treated with tofacitinib.

SIE/HZ risk was highest in patients with ALC <0.5 × 103 cells/mm3, supporting this threshold as clinically relevant for defining increased SIE/HZ risk in Japanese patients with rheumatoid arthritis receiving tofacitinib. However, SIEs and HZ events did not necessarily occur simultaneously with confirmed lymphopenia, preventing conclusions on possible causal relationships being drawn.