The ultrasonographic spectrum of toe dactylitis in psoriatic arthritis: a descriptive analysis

Dactylitis is a hallmark of psoriatic arthritis (PsA). While its assessment is clinical, recently musculoskeletal ultrasonography (MSUS) has been applied to its monitoring. However, the evidence on MSUS application for toe dactylitis is limited. The aim of this study is to characterize the ultrasonographic features of toe dactylitis in PsA.

Patients with PsA and painful toe dactylitis were retrospectively identified from clinical records. Demographic and clinical variables were analyzed. Ultrasound images of the affected toe, allowing the assessment of grey scale (GS) and power Doppler (PD) were collected, to evaluate tenosynovitis, soft tissue oedema (STO), synovitis of metatarsophalangeal (MTP), proximal and distal interphalangeal (PIP, DIP) joints (all graded 0-3), and peritendonitis (PTI) at the MTP and PIP (graded 0-1). Clinical and ultrasonographic features were analyzed through descriptive statistics.

The study included 26 patients (30 toes) of which 9 (34.5%) females, with mean (sd) age of 46.8 (11.73). All but one patient had an oligoarticular phenotype. Tenosynovitis was the most frequent lesion, with GS abnormalities in 27/30 toes (90%) and PD in 25/30 (83.3%). STO was common (GS in 28/30 (93.33%) toes and PD in 20/30 (66.66%)). Synovitis was less common (63.33%, 46.66% and 33.33% of MTPs, PIPs and DIPs, respectively), while PTI was uncommon, with no patient presenting with PD.

Ultrasound showed different elementary lesions in toe dactylitis confirming the complexity of this manifestation also at foot. These findings represent a first step toward the development of further imaging studies assessing toe dactylitis in PsA. Key Points • Tenosynovitis and soft tissue oedema were the most common ultrasonographic elementary lesion in acute toe dactylitis in psoriatic arthritis. • Synovitis was less frequent and peritendonitis was very uncommon. • Musculoskeletal ultrasound confirms the presence of multiple lesions in painful toe dactylitis, confirming the complexity of this manifestation.