Diabetes insipidus secondary to nivolumab-induced neurohypophysitis and pituitary metastasis.

SUMMARY: A 62-year-old patient with metastatic hypopharyngeal carcinoma underwent treatment with nivolumab, following which he developed symptoms suggestive of diabetes insipidus. Nivolumab was stopped and therapy with methylprednisolone was started. During corticosteroid therapy, the patient presented himself in poor health condition with fungal infection and glycemic decompensation. Methylprednisolone dose was tapered off, leading to the resolution of mycosis and the restoration of glycemic compensation, nevertheless polyuria and polydipsia persisted. Increase in urine osmolarity after desmopressin administration was made diagnosing central diabetes insipidus as a possibility. The neuroradiological data by pituitary MRI scan with gadolinium was compatible with coexistence of metastatic localization and infundibulo-neurohypophysitis secondary to therapy with nivolumab. To define the exact etiology of the pituitary pathology, histological confirmation would have been necessary; however, unfortunately, it was not possible. In the absence of histological confirmation, we believe it is likely that both pathologies coexisted. LEARNING POINTS: A remarkable risk of endocrine immune-related adverse events (irAEs) during therapy with checkpoint inhibitors exsists. In order to ensure maximum efficiency in the recognition and treatment of endocrine iRAes related to immune checkpoint inhibitors, multidisciplinary management of oncological patients is critical. The pituitary syndrome in oncological patients who underwent immunotherapy represents a challenge in the differential diagnosis between pituitary metastasis and drug-induced hypophysitis. This is the first case, described in the literature of diabetes insipidus in a patient suffering from nivolumab-induced infundibulo-neurohypophysitis and anterohypophyseal metastasis.