Endocrine Abstracts

A 26-year-old man presented with a 3-month history of polydipsia, polyuria and nocturia. Physical examination was unremarkable. Random blood glucose was 5.1 mmol/l, sodium 147 mmol/l, serum osmolality 297 mOsm/kg, urine osmolality 81 mOsm/kg. A water deprivation test confirmed cranial diabetes insipidus. Magnetic resonance imaging (MRI) of his pituitary gland revealed nodular thickening of the pituitary stalk suggestive of inflammatory or neoplastic aetiology. He also complained of pain in his right ankle for which he had an X-ray which showed diffuse permeative abnormality with periosteal reaction. MRI scan of his legs and a bone isotope scan revealed involvement of several other parts of his skeleton. Computerised tomography scan of his chest, abdomen and pelvis did not show any visceral involvement or lymphadenopathy. A bone biopsy of his right femur revealed diffuse infiltration of the medullary space by foamy histiocytes in a background of fibrosis and chronic nonspecific inflammation. The immunostaining of the foamy cells was negative for S100 and positive for CD68. The findings confirmed a diagnosis of Erdheim-Chester disease. He was commenced on desmopressin and further testing revealed low testosterone and GH deficiency.

Erdheim-Chester disease is a rare non-Langerhans form of histiocytosis characterised by xanthomatous infiltration of tissue with foamy histocytes with positive immunohistochemical staining for CD68 and negative for CD1a and in 80% of cases negative for S100 protein. Bone pain is the most common symptom, mainly affecting the lower limbs. It predominantly involves the skeletal system but other organs are involved including the pituitary gland typically causing diabetes insipidus. The first line of treatment is interferon alpha with a 5-year survival of 68%.