Musculoskeletal ultrasound discriminating camptodactyly-arthropathy-coxa vara-pericarditis syndrome and juvenile idiopathic arthritis.

OBJECTIVE

Camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) and juvenile idiopathic arthritis (JIA) both feature joint effusions. This study aimed to identify preliminary MSUS-based criteria that may help discriminate children with CACP from those with polyarticular JIA.

METHODS

A retrospective multicentre analysis of MSUS images from children with genetically confirmed CACP or a diagnosis of active polyarticular JIA was performed. Joint and tendon findings were evaluated using qualitative B-mode (BM) and Doppler-mode (DM) assessment and graded semi-quantitatively (0-3) according to OMERACT definitions.

RESULTS

All four children with CACP showed symmetrical joint involvement, with effusion present in 46/46 scanned joints and no intrasynovial hypervascularity (median DM = 0). In the JIA cohort (n = 6) 16/42 joints had asymmetric effusions, of which 56% showed intrasynovial hypervascularity (median DM = 1). All 16/16 scanned tendons in the CACP group showed no DM signal, whereas hypervascularity was observed in 7/8 affected tendons in the JIA cohort. Hyperechoic foci, suggestive of increased synovial fluid viscosity, were present in 18/46 (39%) affected joints in the CACP group compared to 1/16 (6%) in the JIA cohort.

CONCLUSION

CACP is characterised by symmetrical large-joint effusions with hyperechoic foci and absence of intrasynovial DM signal, in contrast to inflammatory findings in JIA. These features may support early differentiation of CACP from JIA and therefore prompt earlier specific diagnostics, including genetic testing.