Combined Hypophysitis and Type 1 Diabetes Mellitus Related to Immune Checkpoint Inhibitors

CONTEXT: The occurrence of multiple endocrinopathies due to immune checkpoint inhibitors (ICIs) is a relatively common adverse event. However, the occurrence of a combination of hypophysitis and type 1 diabetes mellitus (T1DM) is extremely rare, and its clinical features are unclear. OBJECTIVE: We comparatively analyzed the clinical features of this combination and each individual ICI-induced endocrinopathy. METHODS: We reported 3 cases that we encountered and reviewed previously reported cases of patients with combined hypophysitis and T1DM due to ICIs. RESULTS: Anti-programmed cell death-1 (anti-PD-1) antibodies were prescribed to all 3 cases. The duration from ICI initiation to the onset of endocrine disease was 12 to 48 weeks. Several human leukocyte antigen (HLA) haplotypes that have disease susceptibility to hypophysitis were detected in all 3 patients. With the 17 previously reported cases, combined endocrinopathies were more common in men (85%). The onset age was in the 60s for both combined and single endocrinopathies. Anti-PD-1 antibodies were used in most of the cases (90%). The time from ICI initiation to the onset of endocrinopathies was 24 (8-76) weeks for hypophysitis and 32 (8-76) weeks for T1DM in patients with combined endocrinopathies, which was not significantly different from that for each single endocrinopathy. CONCLUSION: We presented 3 cases of patients with combined endocrinopathies of hypophysitis and T1DM that may have been caused by anti-PD-1 antibodies. There was no difference in the time from ICI initiation to the onset of endocrinopathies between combined and single endocrinopathies. Further case accumulation and pathogenic investigations are required.