Langerhans Cell Histiocytosis of the CNS Presenting With Diabetes Insipidus and Fever of Unknown Origin: A Case Report

Langerhans cell histiocytosis (LCH) is a rare neoplastic disorder caused by clonal proliferation of Langerhans cells.LCH of the CNS can involve the suprasellar region and typically presents with headache, fever of unknown origin, and diabetes insipidus.A high index of suspicion is therefore needed when encountering such a presentation.We present the case of a 32-year-old woman who presented mainly with fever of unknown origin, frontal pressure headache, episodes of vomiting, and intermittent right-sided paresthesia.Her clinical course began with a diagnosis of fever of unknown origin approximately two years earlier.Initial evaluation revealed hypernatremia, prompting an endocrine referral.Subsequent investigation at the referring institution established a diagnosis of diabetes insipidus, with brain MRI demonstrating a suprasellar lesion.Due to prolonged hospitalization, the patient was subsequently referred to a tertiary care center, where MRI demonstrated a well-defined, enhancing, T2-isointense lesion centered in the hypothalamic-chiasmatic region, measuring approximately 16 × 17 × 12 mm (anteroposterior, transverse, and superoinferior dimensions), with adjacent edema in the hypothalamic region and optic tracts.At that point, she had diagnoses of diabetes insipidus, primary hypothyroidism, and diabetes mellitus, the latter noted in the context of obesity.Her medications included desmopressin, insulin aspart, insulin degludec, and levothyroxine.Biopsy confirmed CNS LCH, with immunohistochemistry revealing a BRAF V600E mutation.The patient underwent surgical debulking via right frontal craniotomy, leaving a residual mass measuring 9 × 9 × 7 mm.She was subsequently started on vemurafenib, a targeted BRAF inhibitor.No radiation therapy was administered, and she remains on an intermittent dosing schedule (one week on, one week off) under continued neurosurgical follow-up nearly two years after treatment initiation.This case shows that LCH may present with unexpected clinical features.Because the differential diagnosis can be complex, recognizing the typical and atypical clinical presentations of CNS LCH is crucial for early diagnosis, as CNS involvement can be easily missed.