Clinical Features and Outcomes of Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid (DPP4i-Associated BP) in Thai Patients

The use of dipeptidyl peptidase-4 inhibitors (DPP4i) appears to be associated with a small but significantly elevated risk of bullous pemphigoid (BP). Although the pathogenic mechanism of DPP4i-associated BP remains unclear, this adverse event is reported with multiple gliptins, suggesting a class effect. However, previous studies from various countries showed that vildagliptin had been implicated in most cases. The aim of this study was to illustrate a case series of DPP4i-associated BP in Thai patients. We conducted a retrospective study from consecutive cases of BP in people with type 2 diabetes mellitus (T2DM) from January 2008, the year in which the first DPP4i was introduced in Thailand, until December 2019. During the study period, 10 BP patients with T2DM were identified. A total of 5 DPP4i-associated BP (3 on vildagliptin, 1 on linagliptin, and 1 on sitagliptin) were found. All patients were male with a mean age at BP development of 80.4 years (73-86 years). All patients had a long-standing duration of diabetes (median duration 34 years), and mean A1C was 7.5 +/- 1.4%. The median time to BP development after the introduction of DPP4i was 64 months (range 20-128 months). The severity of BP was classified as mild in 2 cases. In all cases, the association between the drug intake and BP onset was classified as "possible" according to the Naranjo causality scale. All of the patients continued taking DPP4i after BP diagnosis, and one patient died of lung cancer 18 months after BP diagnosis. Only 2 patients could achieve complete remission at least 2 months after stopping DPP4i. Our case series demonstrated a potential link between DPP4i and the development of BP, which mainly occurred in very elderly male patients. The latency period from an introduction of DPP-4i could be several years, and the clinical course after DPP4i discontinuation varied. Clinicians prescribing DPP4i should be aware of this association and consider stopping this medication before a refractory disease course ensues.