Learning disabilities can be defined as neurologically based processing problems that interfere with basic learning skills such as understanding, reading or counting, but also with higher-level skills such as space and time coordination. Adaptive learning systems are usually not designed to take into account learning disabilities, even if the need for enhancing support of learners with disabilities is more and more important within nowadays society. We first identify the set of learning disabilities to consider in an accessible adaptive learning system; then a content model is proposed integrating the matching abilities and extending a standard to ensure interoperability with existing solutions. Finally, a case study is presented to apply the proposed model in order to identify a learning object designed to support math skills at elementary school.