A case of lymphocytic infundibuloneurohypophysitis: histophathological studies

A 57-year-old woman presented with 2-year history of polyuria and polydipsia. Hormonal studies revealed almost normal anterior pituitary function and central diabetes insipidus. Magnetic resonance imaging showed thickening of the pituitary stalk and enlargement of the neurohypophysis without high intensity of the posterior lobe on T1-weighted images, which were compatible with lymphocytic infundibuloneurohypophysitis. Transsphenoidal biopsy was done and histological examination disclosed moderate fibrosis and lymphocytic infiltration not only in the posterior pituitary, but also in the adjacent anterior pituitary part of the gland. The lymphocytes both in the anterior and posterior pituitary were mainly T cells that were positive for UCHL 1, CD 3, and CD 8. Immunofluorescence of frozen tissue detected immunecomplex deposition in small vessels and the interstitium. These findings suggested that allergic reactions may play an important role in the pathogenesis of lymphocytic infundibuloneurohypophysitis.