Endocrine Abstracts

Introduction: Erdheim-Chester disease is a rare form of non-Langerhans’ cell histiocytosis characterised by foamy histiocyte infiltration with multi-systemic manifestations. Roughly 550 cases have been described in the literature, most frequently affecting men aged 40-60. Bony pain is the most common symptom, resulting from osteosclerotic lesions of the long bones of the lower limbs. Extra-skeletal manifestations are varied and include diabetes insipidus resulting from pituitary infiltration.

Case History: A 65-year-old female presented in 2010 with a short history of polyuria and polydipsia. She had a fluid intake of 7-8 litres, passing equal amounts of dilute urine. Cranial diabetes insipidus was confirmed with the hypertonic saline test. Baseline serum osmolality increased from 295 mOsmol/kg 313 mOsmol/kg. Peak AVP level was 0.4 pmo/l from a baseline of 0.3 pmo/l. There was prompt concentration of urine with Desmopressin (baseline urine osmolality 63 mOsmol/kg increased to 580 mOsmol/kg) confirming cranial diabetes insipidus. Short Synacthen test was normal. The patient had a history of primary hypothyroidism treated with Levothyroxine but had no other systemic symptoms. Idiopathic cranial diabetes insipidus was diagnosed in the absence of a structural pituitary lesion on MRI scanning. X-Rays in 2021 for persistent knee pain showed radiological features and lesions consistent with Erdheim-Chester disease, confirmed on bone biopsy. 10 years after initial presentation, it was established that the diabetes insipidus was secondary to Erdheim-Chester disease.

Discussion: Erdheim-Chester disease is a rare cause of cranial diabetes insipidus. Due to its rarity and non-specific multi-systemic manifestations, there is often a diagnostic delay. It should be considered in patients presenting with cranial diabetes insipidus of unclear aetiology alongside bony pain or other unexplained multi-systemic complaints.