Unilateral bony ankylosis of the temporomandibular joint in a case of ankylosing spondylitis.

BACKGROUND: Ankylosing spondylitis (AS) is a chronic inflammatory disease with multiple articular and para-articular involvement that has a predilection for the axial skeleton. In spite of its high prevalence, ankylosis secondary to AS is a rare condition. CASE REPORT: A 31-year-old male diagnosed with AS was referred for computed tomography (CT) of the temporomandibular joint (TMJ) due to severe mouth opening limitation. The patient had a 16-year medical history of AS and sought assistance due to TMJ pain and incapacity to open his mouth. RESULTS: Previous bony scintigraphy revealed involvement of the spine, sacroiliac joints, right knee, and left TMJ. Magnetic resonance imaging revealed erosion of the left condyle and posterior slope of the articular eminence, and a mass of heterogeneous signal intensity between these structures. The left condyle also presented sclerosis/edema of the bone marrow and the disk could not be identified. Sagittal and coronal CT images showed moderate alterations of the TMJ on the right side. On the left side, the images displayed markedly eroded condyle and mandibular fossa, and a bony mass resulting in ankylosis of the osseous components of the joint. CONCLUSION: TMJ ankylosis in AS patients is rare and very few reports have presented imaging features of the condition through advanced diagnostic techniques.