This study is being done to answer the following question: What are the supportive care needs of informal caregivers of people with Erdheim-Chester disease and other histiocytic diseases?

Inclusion Criteria:

• Self-identified informal caregiver (family member or friend who provides unpaid support) for a patient with Erdheim-Chester Disease (or LCH, RDD, or JXG for the exploratory aim).
• Proficiency to complete study assessments in English, evaluated at the time of consent.
• Age 18 or over.

Exclusion Criteria:

• Participant unwilling to sign consent.
• Participant unable to complete web-based assessments.

A target sample of 120 ICs of patients with Erdheim-Chester Disease will be enrolled in this study. Additionally, a target sample of 50 ICs of patients with other histiocytic disorders will be enrolled.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.