Pure Lymphocytic Infundibuloneurohypophysitis Caused by the Rupture of Rathke's Cleft Cyst: Report of 2 Cases and Review of the Literature.

The major symptoms that are caused by Rathke's cleft cysts (RCCs) are visual disturbances, headaches, and endocrine insufficiencies. Among these symptoms, the endocrine insufficiencies are thought to result from the spreading of inflammation that is induced by the cyst contents onto the pituitary gland or the compression of the gland and the pituitary stalk by RCCs. Here, we present 2 rare cases with lymphocytic infundibulohypophysitis with the sudden onset of headaches and subsequent diabetes insipidus (DI). Magnetic resonance imaging revealed remarkable swelling of the pituitary gland with a small mass that was located between the anterior and the posterior lobe of the pituitary gland. Transsphenoidal surgery was performed to remove the mass, and pathological examinations of the cyst wall demonstrated that the epithelial tissue of the RCC and the posterior lobe were affected by massive lymphocytic infiltration. The clinical courses and pathological results of these patients strongly suggested that the rupture of the RCC onto the posterior lobe caused the lymphocytic hypophysitis. Postoperatively, the DI could be controlled with a smaller amount of anti-diuretic hormone replacement compared to that required preoperatively.