Page 29 - MRS Abstracts March 2023

Prevalence of Lymphopenia in patients on Janus Kinase- Inhibitors
Naina Naina1 Nadeem Mir1
Hafis Muhammed1 Srinivasan Venkatachalam1
Rheumatology Department, The Royal Wolverhampton NHS Trust
Introduction:
Janus Kinase (JAK) inhibitors have gained prominence in the treatment of autoimmune rheumatic diseases. However, as new safety concerns arise surrounding these drugs, there is a growing sense of caution in their prescription. One such concern involves the development of lymphopenia, a known adverse effect associated with certain JAK inhibitors. Lymphopenia has implications in the pathogenesis of certain cancers and susceptibility to infections.
The drug Summary of product characteristics (SmPC) for Tofacitinib and Baricitinib says to interrupt treatment if absolute lymphocyte count (ALC) is less than 0.5 and decrease the dose of tofacitinib if ALC is less than <0.75. We had a patient who had severe lymphopenia with Baricitinib who succumbed to pneumocystis pneumonia. Thus, we aimed at investigating occurrences of JAK-related lymphopenia.
Methods:
We retrospectively reviewed medical records of 25 each of initial cohort of patients started on Tofacitinib, Baricitinib and Upadacitinib. Lymphopenia was categorized into three levels based on the ALC:
• Mild lymphopenia: ALC between 0.7 and 1.49 x 10^9/L
• Severe lymphopenia: ALC ranging from 0.5 to 0.7 x 10^9/L
• Very severe lymphopenia: ALC less than 0.5 x 10^9/L