Herpes zoster in the context of immune reconstitution inflammatory syndrome in patients with rheumatic diseases: a single-center retrospective study

Immune reconstitution inflammatory syndrome (IRIS) experienced in rheumatology practice is diverse and includes opportunistic infections such as herpes zoster (HZ). This study aimed to explore the risk of HZ in patients with rheumatic diseases in the perspective of IRIS. The study retrospectively reviewed the clinical courses of 20 patients with HZ and investigated the IRIS triggers such as the reduction or discontinuation of immunosuppressive drugs within 3 months and coronavirus disease 2019 (COVID-19) vaccination within 4 weeks prior to HZ development. Disease activity of the underlying rheumatic disease at HZ onset was evaluated using the physician's global assessment. Thirteen patients developed HZ after reducing or discontinuing immunosuppressive drugs, with mild and stable disease activity. In four of these cases, disease activity increased after dose reduction or discontinuation, and HZ subsequently developed. Two of the seven patients who did not reduce or discontinue immunosuppressive drugs received the COVID-19 vaccination. Fifteen patients (75%) had at least one of the two IRIS triggers. Four of the five patients who developed HZ without any IRIS triggers were at HZ risk. To conclude, IRIS, caused by the reduction or discontinuation of immunosuppressive drugs, may be involved in the development of HZ in rheumatology practice.