The patient was drowsy, dysarthric and confused. She had panhypopituitarism including low cortisol and cranial diabetes insipidus. A contrast-enhanced CT of the chest, abdomen, and pelvis was unremarkable. Negative bone scan. Bilateral external ventricular drains were placed to treat the hydrocephalus with a concurrent brain and dural biopsy.

Erdheim-Chester disease, a non-Langerhan cell histiocytosis, was confirmed by foci of small foamy macrophage infiltrates in the parenchyma and dura on pathology in correlation with the clinical context.

Tuberculosis was ruled out by multiple repeated negative cultures. Neurosarcoidosis was eliminated due to normal angiotensin converting enzyme and negative CT chest, abdomen and pelvis study.There were no oral ulcers and the brain biopsy was negative for neuro-Behcet which is an idiopathic chronic inflammatory vasculitis. CNS lymphoma and gliomatosis cerebri were also ruled out on cranial biopsy.

Isolated involvement of the neuroparenchyma is rare in Erdheim-Chester disease.The key MR diagnostic features in the brain are involvement of the hypothalamic-pituitary axis hypointense on T2 with nodular thickening and enhancement post contrast, pachymeningeal thickening, and enhancement. Intra-axial involvement with abnormal signal intensities is very rarely noticed in the midbrain and pons.