Spontaneous regression of isolated neurohypophyseal langerhans cell histiocytosis with diabetes insipidus.

In pediatric and adolescent patients, the most common causes for a thickened pituitary stalk with central diabetes insipidus are germ cell tumors, lymphocytic infundibuloneurohypophysitis (LIN), and Langerhans cell histiocytosis (LCH). We describe here a 13-year-old girl who had an abrupt onset of polyuria and polydipsia. Magnetic resonance imaging of the brain revealed thickening of the pituitary stalk, and loss of the physiological hyperintense signal of the posterior pituitary gland. Based on a histopathology, she was diagnosed as having LCH. Another LCH lesion was not detected. The prognoses for LCH patients with single-system and single-site are generally good so we decided on only simple observation. The lesion spontaneously regressed 3 months later, resembling a typical self-limiting course of LIN. In conclusion, the present case suggests that 1) radiological differential diagnosis between LIN and LCH is so difficult that histological confirmation is crucial for correct diagnosis, 2) some past cases of histologically-unconfirmed LIN can include LCH, 3) solitary neurohypophyseal LCH can shrink spontaneously up to near remission level.