Background: This paper explores a concept of an app that aims to improve the care of patients suffering from a rare disease. The aim of this work is to identify patient needs and specify corresponding app modules. Further research and product development can be performed using this concept. Importance and Objectives: The work is guided by the question: How can digital technologies be used to impact rare diseases? Additionally, the question of how far the needs of people affected by a rare disease can be generalised, and what has to be addressed specifically for a particular disease will be explored. In order to understand the current technology, the state and scope of existing digital solutions for rare diseases will be considered. Methods: Initially, a literature review was conducted. Based on this a theoretical model was created. The model was validated in eight expert interviews and the results used for updating the model. Findings and Conclusion: The greatest potential to influence the quality of care and life through an app exists in the area of psychological and information needs. It is possible to address many needs of patients with rare diseases by universal app modules. By adding some specific modules, most needs can be covered. This work can be used as a starting point for a combined product development of health apps for many rare diseases.