Neurodegenerative (ND) type of Central Nervous System (CNS) Langerhans Cell Histiocytosis (LCH) is a very rare disease. We report a case of a pregnant teenager found to have central diabetes insipidus and T2 FLAIR contrast-enhancing lesions on MRI brain. Extensive workup including brain biopsy showed inflammation and concern for LCH. Progressive neurological symptoms prompted the start of low-dose cytosine arabinoside chemotherapy. Her symptoms and serial MRI brain scans showed a complete tumor response to the chemotherapy. Off-therapy tumor recurrence prompted the use of MAPK (mitogen-activated protein kinase) pathway agent Trametinib with good response.
