A Study of Memory, Thinking, and Brain Imaging in Adults With Histiocytosis

Inclusion Criteria:

- Age greater than or equal to 18 years.

- Fluency in English

- Diagnosis of a histiocytic disorder as determined, in the opinion of the study PI, by
a corroborating constellation of histopathology, clinical, and/or radiologic findings.

- Will undergo Standard of Care MRI.

Exclusion Criteria:

- Known intracranial involvement of histiocytosis (including dura, leptomeninges and
brain parenchyma)

- Prior stroke or intracranial hemorrhage

- Other (non-histiocytic) intracranial neoplasm or neurological disorder deemed by the
PI or Co-PI to confound neuroimaging studies (e.g., demyelinating disease)

- Existing diagnosis of a psychiatric disorder or untreated mood disturbance

- Existing diagnosis of a neurodegenerative disease, such as Alzheimer's disease

- Chronic or daily excessive alcohol consumption as determined by the PI.

- History of chronic use of corticosteroids, defined as continuous treatment for six
months or longer at any time in the past

- History of severe claustrophobia or other contraindications to patient SOC brain MRI

- Prior intravenous cytarabine or cladribine

- Other current or prior treatments (e.g., high-dose chemotherapy for a different
cancer) deemed by the PI or Co-PI to confound imaging studies or cognitive performance