Delayed lymphocytic infundibuloneurohypophysitis following successful transsphenoidal treatment of Cushing's disease

Lymphocytic infundibuloneurohypophysitis is a rare disorder in which neurohypophyseal function is impaired by an autoimmune process. Although several etiologies for this rare entity have been suggested, its occurrence following transsphenoidal adenomectomy has not been reported. A 20-year-old man presented with diabetes insipidus - seven years after successful transsphenoidal microadenomectomy for Cushing's disease, first diagnosed at the age of 13. Seven years later, he developed fairly rapid onset of polydipsia and polyuria. Magnetic resonance imaging demonstrated swelling of the posterior pituitary gland with thickening of the pituitary stalk. Endocrinological evaluation revealed neurohypophyseal dysfunction without the adenohypophysis being affected. On the basis of these findings, a diagnosis of lymphocytic infundibuloneurohypophysitis was made. The mass lesion of the posterior pituitary resolved after the administration of corticosteroids for two months and no operation was required. Lymphocytic infundibuloneurohypophysitis should be considered in the differential diagnosis of pituitary mass lesions following transsphenoidal surgery, especially when the mass is confined to the posterior pituitary gland with neurohypophyseal function being compromised.