Anti-pituitary-specific
transcription factor 1 (PIT-1)
hypophysitis (anti-PIT-1 antibody syndrome) is a
thymoma-associated
autoimmune disease characterized by acquired
growth hormone (GH),
prolactin (PRL), and
thyrotropin (
TSH) deficiencies due to autoimmunity against PIT-1. Ectopic expression of PIT-1 in the
thymoma plays a causal role in development of the disease. Here, we report 2 cases of anti-PIT-1
hypophysitis exhibiting as a form of
paraneoplastic syndrome with conditions other than
thymoma. A 79-year-old woman (case 1) and an 86-year-old man (case 2) were referred with a suspicion of anti-PIT-1
hypophysitis because of acquired GH, PRL, and
TSH deficiencies. Case 1 was complicated by
diffuse large B-cell lymphoma (DLBCL) of the bladder and case 2 was diagnosed with
malignancy with multiple
metastases of unknown origin. Because circulating anti-PIT-1 antibody was detected, both patients were diagnosed with anti-PIT-1
hypophysitis. Circulating PIT-1-reactive T cells were detected in case 1 via
enzyme-linked immunospot (ELISPOT) assay. Interestingly, the PIT-1
protein was ectopically expressed in the DLBCL cells of case 1, whereas DLBCL tissues derived from patients without anti-PIT-1
hypophysitis were negative for PIT-1. In case 2, the materials were not available because of best supportive care was under way. These data show that anti-PIT-1
hypophysitis is associated not only with
thymoma but also with other
malignancies. Additionally, the ectopic expression of PIT-1 in the DLBCL tissues and presence of PIT-1-reactive T cells suggested that the underlying mechanisms were similar to those observed in
thymoma. Thus, anti-PIT-1
hypophysitis is defined as a form of
paraneoplastic syndrome.