Fibrodysplasia Ossificans Progressiva (FOP) is a connective tissue disorder that progressively affects tendons, ligaments, aponeurosis, fasciae and muscles which undergo fibrous cell proliferation that progresses to mature bone. It has a prevalence of 1 case per 2 million habitants, having reported less than 1000 cases worldwide. In the maxillofacial region, it might originate extra-articular temporomandibular ankylosis by ossification of ligaments, muscles of the mastication, head and a neck muscles; the most commonly affected are the masseters and sternocleidomastoids. The purpose of this article is to review the Fibrodysplasia Ossificans Progressiva (FOP) and to present the case of a 12-year-old male patient with FOP that causes extra-articular temporomandibular ankylosis. There is no effective proven treatment or prevention and the life expectancy of these patients approaches the 40 years of age, so the management of patients with FOP must be performed with a multidisciplinary approach in which the various health professionals work in a coordinated and joint way to offer a better quality of life to these patients and thus better understand the progression of the disease.