Patient and public involvement (PPI) is a practice for involving future users in the design, development, and research of health technologies. There is increasing interest and demand for PPI, but little evidence based methodological support for integrating PPI in agile development processes. Multiple sclerosis (MS) is a chronic condition that severely impacts the lives of patients and requires active patient involvement. In this paper, we present the results of a case study, examining the adoption and integration of PPI into the development of a digital therapeutics solution for MS. The results highlight five critical phases that proved to be challenging: selecting patient participants, onboarding of patient participants and employees, framing tasks for patient participants, communication between patient participants and the rest of the development team, and reimbursements. The results are useful in creating evidence-based guidelines and methods for supporting the adoption of PPI.