Lymphocytic Panhypophysitis Resulting in Panhypopituitarism in a Dog

A 3 yr old intact male Doberman pinscher was referred with chronic diarrhea, severe polyuria-polydipsia, and behavioral changes for 2 wk. Biochemical abnormalities were consistent with central diabetes insipidus, hypothyroidism, and hypoadrenocorticism. Brain MRI and cerebrospinal fluid analysis raised suspicion for lymphocytic hypophysitis and meningitis, later confirmed histologically. Immunosuppressive steroid therapy and hormonal supplementation were implemented, resulting in a marked clinical improvement. Brain MRI at a 3 mo follow-up showed a resolution of inflammatory lesions along with pituitary atrophy. The patient was euthanized 4.5 mo following diagnosis because of uncontrolled aggressiveness. Lymphocytic hypophysitis (LHP) is a rare autoimmune condition in people and dogs, often accompanied by total or partial pituitary hormonal deficiency. This is the first case of histologically confirmed canine LHP with documented clinical and biochemical response to medical management. As described in people, LHP should be considered as a differential diagnosis for pituitary lesions. Although the overall prognosis of this disease remains guarded to poor, early diagnosis and adequate immunosuppressive treatment might improve the outcome.