Osteochondroma of coronoid process: a rare etiology of jacob disease.

Jacob disease is a rare entity consisting of the formation of a pseudojoint between the inner surface of the zygoma and the coronoid process. This requires constant contact between the two implicated surfaces. It can be achieved by two mechanisms: one by an enlarged coronoid process and two by an anterior displacement of the coronoid process caused by a temporomandibular joint (TMJ) disorder. Although von Langenbeck described coronoid process hyperplasia in 1853, Oscar Jacob was the first author to describe the pathology in 1899. Since then, only a few cases have been published in the literature. The authors report a rare case of Jacob disease caused by an osteochondroma of the coronoid process, which is even less common, and review the literature.