[Importance of long-term follow-up of diabetes insipidus; from lymphocytic hypophysitis to germinoma].

A case is presented of a 10-year old boy who had a hypothalamic-pituitary axis disorder. He initially presented with diabetes insipidus that progressed to panhypopituitarism. A hidden hypothalamic lesion should be suspected in all these cases, and should be followed up. New lesions were found in the pituitary stem three years later. Although tumor markers were negative, there was an increase in size, and a biopsy was performed. The histopathology reported a Lymphocytic Hypophysitis. There were increases in the tumor markers during the follow-up, thus a second biopsy was performed, with the diagnosis of Germinoma. Lymphocytic Hypophysitis is an uncommon diagnosis in children. Few cases have been reported, and in some cases, they were later diagnosed with Germinoma. We believe this case highlights the importance of the follow-up of children with Central Diabetes Insipidus with a normal MRI, as well as not taking the diagnosis of Lymphocytic Hypophysitis/lymphocytic Infundibular neurohypophysitis as definitive, as it is a rare diagnosis at this age, and could mask a Germinoma, as recorded in some cases.