Clinical features of anti-PIT-1 hypophysitis: A new aspect of paraneoplastic autoimmune condition.

The pathogenesis of anti-pituitary-specific transcription factor 1 (PIT-1) hypophysitis was gradually revealed as cases emerged. Our comprehensive analysis, including all reported cases, identified a new instance of anti-PIT-1 hypophysitis post-immune checkpoint inhibitor therapy. All nine patients exhibited extremely low GH, PRL, and TSH levels; two had a slightly atrophic pituitary gland; four had thymoma, and five had malignant neoplasms of diffuse large B-cell lymphoma (DLBCL) and other origins. Patients with thymoma showed multiple autoimmune diseases. HLA-A*24:02 and/or A*02:06 were present in six and DR53 in five cases analyzed. High anti-PIT-1 antibody titers and ectopic PIT-1 expression in the cytosol and nucleus of the tumor tissues were observed in patients with thymoma or DLBCL, whereas it was exclusively observed in the nuclei of a bladder cancer patient. These findings provide new insights into the pathophysiology of paraneoplastic autoimmune hypophysitis.