Introduction Diabetes insipidus may rarely be due to Langerhans-Cell Histiocytosis (LCH) and is the presenting symptom in 14-15% of patients with LCH.
Clinical case A 46-year-old male presented with typical symptoms of diabetes insipidus on a background of presumed alcoholic steatosis, anxiety and gastro-oesophageal reflux disease. Central diabetes insipidus was confirmed by a water deprivation test. Pituitary biochemistry was otherwise unremarkable, however an MRI demonstrated a thickened, homogenously enhancing pituitary gland and stalk with loss of the pituitary bright spot. A CT demonstrated lytic lesions in the pelvis, [pulmonary micronodular infiltrate in bilateral upper lobes, and liver changes confirmed on MRCP to be a lesion infiltrating hepatic biliary ducts. Biopsy of the bone lesion was non-diagnostic, but lung biopsy eight months post-presentation was consistent with LCH.
The patient was managed with cytarabine chemotherapy for 12 months; an FDG PET scan after three months of treatment revealed no avid lesions. At completion of the course clinical remission was achieved, with the exception of ongoing diabetes insipidus. Seven months after completing chemotherapy, the patient developed hypogonadotrophic hypogonadism requiring testosterone replacement. The remainder of the pituitary biochemistry was unremarkable. His liver function tests continued to be deranged. Gene testing was positive for the BRAF V600E mutation.
Two years following completion of chemotherapy, the patient developed progressive diabetes insipidus necessitating increased doses of desmopressin. He reported subjective cognitive slowing, headaches, nausea, bone pain and fatigue. Cognitive testing was unremarkable and pituitary MRI demonstrated probable size increase of both the pituitary gland and stalk, however repeat PET imaging was normal. Without further therapy, the patient described resolution of all symptoms except diabetes insipidus within five months.
Clinical lessons Langerhans-Cell Histiocytosis should be considered as a differential diagnosis for diabetes insipidus with pituitary stalk thickening. Even with effective systemic therapy, pituitary hormone dysfunction persists indefinitely.