Histopathology of Idiopathic Condylar Resorption Differs From Temporomandibular Joint-Only Juvenile Idiopathic Arthritis.

BACKGROUND

Idiopathic condylar resorption (ICR) is a rare condition of unknown etiology characterized by progressive decrease in volume and pathologic remodeling of a previously normal mandibular condyle. Juvenile idiopathic arthritis (JIA) affecting only the temporomandibular joint (TMJ-only JIA) is characterized by synovitis and destruction of TMJ tissues without involvement of other joints. It is often difficult to differentiate the 2 conditions because they exhibit similar phenotypes.

PURPOSE

To compare histology of resected condylar specimens from patients with ICR and TMJ-only JIA. Specific aims were as follows: 1) to correlate longitudinal clinical data with histopathology of resected condyle specimens and 2) to compare resorption patterns between the 2 disease processes.

STUDY DESIGN, SETTING, SAMPLE: This was a retrospective cohort study of patients treated at the Massachusetts General Hospital from 1999 through 2023.

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLE: Primary predictor variable was the diagnosis (ICR or JIA). Secondary predictor variables included age, gender, race, putative contributing factors, and laboratory studies.

MAIN OUTCOME VARIABLE(S): Primary outcome variable was presence or absence of inflammatory infiltrates in bone and synovial specimens. Secondary outcome variables were structural integrity and morphologic characteristics of the condylar cartilage and bone.

ANALYSES

Spearman correlation was used to assess the relationship between histological scores and age, gender, and possible associated contributing factors. A P value < .05 was considered statistically significant.

RESULTS

Thirty-five subjects (67 specimens) were included in group 1 (ICR). Eight subjects (15 specimens) were included in group 2 (TMJ-only JIA). The histopathologic findings in ICR consisted of severe and irregular cartilage surface disruption, fibrocartilage degeneration, and subchondral bone with no inflammatory infiltrate. Degeneration was observed to begin at the anterior pole of the condyle and progress eventually to total resorption to the sigmoid notch. TMJ-only JIA was notable for more severe condylar degeneration and inflammation in the bone and synovia. There was no specific pattern of degeneration. For both groups, the subject's age, gender, or putative contributing factors did not correlate with the histopathologic scores.

CONCLUSION AND RELEVANCE

These results support the hypothesis that ICR and TMJ-only JIA are distinct clinical entities and can be distinguished by histopathologic findings in the mandibular condyles and synovia.