To present the interesting clinical and neuroimaging findings of CNS Langerhans histiocytosis (LCH) in adult patients.

LCH is a rare multi-organ disease that typically affects children younger than 15 years, but adult-onset LCH usually presents after the fourth decade in a delayed diagnosis fashion. CNS involvement ranges from 3.4-57%. CNS disease can present with focal mass lesions or lesions associated with progressive neurodegeneration.

Case 1: 43-year-old female presented with a vasovagal syncopal episode. MRI brain confirmed a pituitary stalk and neural hypophysis mass with progressive vasogenic edema and mass effect. The patient underwent bifrontal craniotomy and suprasellar mass debulking and pathology revealed a proliferation of histiocytes admixed with lymphocytes, plasma cells, and occasional eosinophils. Histiocytes had a moderate amount of foamy cytoplasm concerning for LCH. Her course was complicated by the development of panhypopituitarism and central diabetes insipidus post-operatively. PET scan showed hypermetabolic left cervical lymph nodes but the fine-needle aspiration of the lymph nodes did not reveal Langerhans histiocytosis pathology. She was initiated on radiation therapy with consideration of chemotherapy with vinblastine with concurrent steroid therapy.

We present two interesting cases of adult-onset, CNS LCH with focal mass lesions in the pituitary/neural hypophysis and posterior fossa with neurodegeneration. In patients with concurrent pituitary dysfunction, LCH should remain in the differential and appropriate therapy should be initiated.