Fibrous dysplasia is a heterogeneous rare bone disorder that is caused by the mosaic distribution of a postzygotic mutation of the GNAS-gene. Although its predominant features are the... Show moreFibrous dysplasia is a heterogeneous rare bone disorder that is caused by the mosaic distribution of a postzygotic mutation of the GNAS-gene. Although its predominant features are the characteristic bony lesions, there is a wide spectrum of FD phenotypes that include a continuously expanding list of extraskeletal manifestations. In line with its wide range of phenotypes, FD is associated with a wide clinical spectrum of symptoms, with pain, deformity, and fractures, leading not only to decreased mobility and function but also significantly impairing Quality of Life. Available surgical and medical therapeutic options should be delivered in a patient-tailored, individualized manner, with full knowledge of their limitations and complications to ensure their most optimal outcome of the various modalities used, singly or in combination. FD is often a multisystemic disease, particularly its most severe forms, so that a multidisciplinary approach is mandatory to achieve the best life-long outcomes. The rarity of FD dictates that all health care professionals involved in the care of FD should invest in international collaboration to provide the necessary power of numbers to address the unanswered questions posed by this ubiquitous disorder, and fulfil the clinical unmet need of developing best clinical practice guidelines for its management. Show less