Lymphocytic hypophysitis (LH) is a rare inflammatory disorder of the pituitary gland and infundibulum most often observed in the setting of autoimmune disease with a variety of clinical and endocrine presentations. The association between lymphocytic hypophysitis and multiple sclerosis has not been reported.

We describe an adolescent boy with polyfocal neurological signs including optic neuritis as well as hypopituitarism and diabetes insipidus related to lymphocytic hypophysitis. His imaging met 2010 McDonald criteria for multiple sclerosis. This diagnosis was further supported by cerebrospinal fluid analysis and a negative evaluation for an alternate diagnosis. Imaging features of lymphocytic hypophysitis include an absent posterior pituitary bright spot with an enlarged cystic pituitary gland, stalk thickening, and improvement with corticosteroid therapy.

Lymphocytic hypophysitis and multiple sclerosis share a common autoimmune pathogenesis, perhaps explaining the co-occurrence of the diseases. The presentation of endocrinologic disturbances such as diabetes insipidus with typical features of a multiple sclerosis attack should prompt further investigation of possible comorbid inflammatory disease involving the hypothalamic-pituitary axis.