Motion-based video games offer great promise in the support of traditional physiotherapy and are currently explored in a growing number of research projects. With a focus on Parkinson’s disease (PD) patients, their therapeutic needs and strong individual differences in capabilities, this work describes an approach to dynamic difficulty adjustments in an exergame tailored for PD patients. The automated ongoing adjustment of the required range of motion, the amplitude parameter, is introduced as an important aspect of such adaptations. Results from a first case study suggest that the approach is viable and appreciated by therapists, yet could benefit from increased flexibility.