Lymphocytic hypophysitis with central diabetes insipidus and subsequent hypopituitarism masking a suprasellar germinoma in a 13-year-old girl

We report a case of central diabetes insipidus, hypothyroidism, and subsequent hypopituitarism due to lymphocytic hypophysitis masking a germinoma in a 13-year-old pubertal girl. Magnetic resonance revealed an enlarged pituitary gland and a mass lesion in the pituitary stalk and inferior hypothalamus. Open cranial surgery of the anterior pituitary showed active hypophysitis with lymphocytic infiltrates but without necrosis. Despite prednisolone therapy, 1 year later an enlarged, irregular cystic mass lesion had developed; in the pituitary stalk and inferior hypothalamus, a endoscopic biopsy revealed germinoma. Lymphocytic hypophysitis in children may be the first sign of a host reaction to an occult germinoma. The diagnosis of central diabetes insipidus with a thickened pituitary stalk requires long-term follow-up to establish the underlying cause.