OBJECTIVES: Patients’ experience of MF/SS-CTCL remains understudied due to the rarity of the condition. Therefore, PatientsLikeMe (PLM) aimed to harness its internal platform, Open Research Exchange (ORE), to explore a novel method of data collection for the concept elicitation phase of PRO development.   METHODS: Members of the MF/SS-CTCL community on PLM were invited to complete an online survey to share their experiences as patients. The 11 open-ended questions intended to elicit descriptions of MF/SS-CTCL quality of life impact, ability to cope and manage their condition, perception of symptoms and treatments, and sources of distress were administered to 21 patients. Of those, 10 participated in a follow-up interview. The data was analyzed by two trained raters and inter-rater reliability was used to validate and confirm their agreement.   RESULTS: The sample (N=21) was predominantly female (67%), all white, and mostly reported MF (76%) rather than SS. The two raters achieved moderate to high inter-rater agreement for the qualitative analysis (0.68-0.80 Cohen’s kappa for the 43 validated codes). Saturation for the sample was reached after 15 patients. Dominant themes that were elicited from the data were social impact (f=27), emotional impact (f=30), impact on daily activities (f=20), coping/management (f=64), severity and burden of symptoms and treatments (f=377, f=291), and overall treatment satisfaction (f=291).   CONCLUSIONS: The online method proved to be an effective tool for understanding the experiences of a population living with a rare condition and complimented the interview data in eliciting dominant themes that were present in the literature. Utilizing ORE as the primary method of data collection, recruitment for this rare condition was found to be easier and faster than traditional methods and the sample size recruited was validated by concept saturation. Therefore, together, the survey and the follow-up interviews proved to be successful in eliciting relevant concepts from patients.