Long-Standing Isolated Autoimmune Hypothalamitis Diagnosed with Endoscopic Transventricular Biopsy

Background Autoimmune hypothalamitis, which is among the causes of acquired central diabetes insipidus, has seldom been described in the literature. This condition is probably provoked by the production of anti-vasopressin-secreting cell antibodies and antihypothalamus antibodies and is often associated with pituitary or polyendocrine autoimmunity. Correct diagnosis and immediate treatment are essential to avoid the progression of the pathologic process. Case Description A woman diagnosed with central diabetes insipidus 12 years ago, who had panhypopituitarism and mild memory deficit, came to our attention. She refused radiologic studies. Magnetic resonance imaging performed in our unit showed a contrast-enhancing hypothalamic lesion. Lumbar puncture was negative for neoplastic markers. We decided to perform a biopsy of the lesion to obtain a histopathologic examination of the tissue and chose an endoscopic transventricular approach to reach the floor of the third ventricle. Autoimmune hypothalamitis was diagnosed and treatment with steroids and azathioprine was started. The lesion size decreased and was stable after 17 months of follow-up. Conclusions The endoscopic transventricular approach has proved to be an effective and safe way to obtain tissue samples for histopathologic examination from a region that is usually difficult to reach; it also gives direct visualization of the lesion, which makes sampling easier. The lesion size decreased after treatment but no clinical improvement was detected, either on the cognitive or on the endocrinologic side.