Description logics are knowledge representation formalisms that are more and more used, in particular because several efficient description logic reasoners are freely available. Fuzzy description logics have been studied in various theoretical work, but few developments of reasoners for them have been realized and made freely available (if any). This paper presents the principles of the development to come of such an inference engine, reusing an inference engine for a classical description logic. This development is based on two main assumptions. The first one is that the fuzzy description logic is obtained by replacing, in a concrete domain of a classical description logic, the binary predicates by fuzzy predicates. The second one is that the inference engine used is composed by two independent reasoners: a concept reasoner and a concrete domain reasoner.