Idiopathic Diabetes Insipidus – a diagnosis of exclusion

G Wordsworth1, K Lonnen1, F Talbot1, R Ion1, N Chavda2

1North Bristol NHS Trust

2University Hospitals Bristol

Abstract: This 34 year old previously fit and well woman underwent a biopsy and curettage of a cystic femoral neck lesion in October 2017.

She then presented to her GP in March 2019 with polyuria and polydipsia. She was referred to the local Endocrine team and a formal water deprivation test confirmed cranial diabetes insipidus. She was commenced on regular desmopressin with the remainder of her pituitary profile intact and with a normal MRI of her pituitary gland. With no knowledge of the previous bone histology, the Endocrine team felt the aetiology of the DI was most likely to be idiopathic and subsequent annual follow-up was unremarkable.

She became pregnant with her second child in February 2020 and was seen in the Joint Antenatal Endocrine Clinic. On close review of the history, her hip problem was felt to be unusual in such a young woman, so we sought the histology from her previous trust. This revealed features in keeping with Langerhan’s cell histiocytosis (LCH) and hence the unifying diagnosis. She was referred to the local specialist Haematology centre who has discussed her regularly at the National LCH Panel.

She is now in her second trimester of pregnancy and has required gradually increasing doses of desmopressin. Regular biochemical assessment has revealed no evidence of progressive pituitary disease and her pregnancy is otherwise uncomplicated.

There is little evidence for how best to manage LCH patients in pregnancy, particularly in those with multi-system involvement. The usual staging investigations and systemic treatments carry significant risks in pregnancy and have to be carefully balanced against the possibility of disease progression whilst waiting until the post-partum period. It is vital to involve multi-disciplinary colleagues from a range of specialties (Endocrinology, Haematology, Obstetrics, Radiology, Neurosurgery and Orthopaedics) in order that we ensure optimal care for each woman in these complex cases.