In this paper we show that some of the evolution tasks in OpenMRS, a health information system, may require the invasive modification of interfaces and implementations in order to offer an appropriate modularization. We introduce a new composition framework in Java that supports the definition of expressive pattern-based invasive compositions. Fur thermore, we show that the composition framework allows us to concisely define an evolution scenario of OpenMRS that supports the consolidation of patient data from differ- ent remote instances.