Jacob's disease: report of a rare case and literature review.

Jacob's disease is a rare condition consisting of pseudojoint formation between enlarged coronoid process and the inner surface of the zygoma. The authors report a 45-year-old female patient who presented with limited mouth opening (5 mm) and swelling of the left zygoma. No temporomandibular joint disease was diagnosed. 3D computed tomography images showed a mushroom-shaped coronoid growth with pseudojoint formation medial and superior to the zygomatic arch. Under general anaesthesia, coronoidectomy was carried out through a combined extraoral and intraoral approach. Histopathological examination revealed normal trabecular bone covered with hyaline cartilage. To the best of the authors' knowledge this case is the fifth typical mushroom-shaped Jacob's disease; only four similar cases have been reported. A review of the literature revealed only 39 histologically proved cases of Jacob's disease cases up to 2010. Aggressive physical treatment was given to improve function and maximum mouth opening, which had increased to 40 mm at 3 months follow-up. The literature concerning this condition's aetiology, pathogenesis, clinical characteristics, diagnosis, and treatment is reviewed.