Dactylitis in Psoriatic Arthritis: Ultrasound Semiotics
According to EFSUMB recommendations, psoriatic arthritis (PsA) is characterized by enthesitis, tenosynovitis, and dactylitis alongside synovitis, and all these manifestations are well detected on ultrasound examination. Ultrasound detects both articular and periarticular inflammation in early and established disease; the obtained data correlate with clinical activity and are sensitive to dynamics during therapy.
Ultrasound Components of Dactylitis
Dactylitis in PsA represents a combination of several inflammatory changes detectable within a single finger. These include synovitis of joints, tenosynovitis of flexor tendons, and enthesitis. In tenosynovitis, the significance is attributed to the peritendinous hypoechoic rim (Breidahl WH et al., 1998).
Activity Assessment and Doppler Imaging
Color Doppler is used to determine synovial activity. When examining superficial joints, minimal transducer pressure should be applied, especially during Doppler imaging, to avoid masking underlying hyperemia. The main question in interpretation is whether the degree of synovitis exceeds what would be expected for the existing joint damage; if the answer is positive, inflammatory or crystal arthritis should be considered.
Differential Diagnosis
A "spectrum of five targets" of ultrasound signs of psoriatic arthritis has been described (Gutierrez M et al., 2010). Ultrasound signs at the level of metacarpophalangeal joints are significant in differential diagnosis between rheumatoid and psoriatic arthritis (Gutierrez M et al., 2011). When septic arthritis or crystal arthropathy is suspected, joint fluid aspiration is indicated.
Visualization Optimization
In inflammatory arthritis, ultrasound helps distinguish normal bone notch from erosion, for which comparison with the contralateral side is recommended. Transducer and joint movement (e.g., interphalangeal joint flexion) improves cartilage visualization.
Frequently asked questions
What components of dactylitis are visible on ultrasound in PsA?
Synovitis, tenosynovitis, and enthesitis; ultrasound detects both articular and periarticular inflammation (EFSUMB, 2022).
How should inflammatory activity be assessed?
Using color Doppler to determine synovial activity; minimal transducer pressure should be applied to superficial joints to avoid masking hyperemia.
What helps differentiate PsA and RA?
Ultrasound signs at the level of metacarpophalangeal joints (Gutierrez M et al., Ann Rheum Dis, 2011).
What finding is characteristic of tenosynovitis?
Peritendinous hypoechoic rim (Breidahl WH et al., 1998).
When is joint aspiration indicated?
When septic arthritis or crystal arthropathy is suspected (Griffith, 2025).