S07:5 | Ankle ultrasound patterns may in the identification of Löfgren’s syndrome in patients with acute-onset erythema nodosum

Davide Corradini¹, Alberto Floris¹, Andrea Carta², Mattia Congia¹, Elisabetta Chessa¹, Matteo Piga¹, Alberto Cauli¹. | ¹Rheumatology Unit, AOU and University of Cagliari, Cagliari, Italy; ²Department Economics and Business, University of Cagliari, Cagliari, Italy.

Background. In this study, we performed ultrasound (US) evaluation of the ankles in patients with acute-onset erythema nodosum (EN) and joint symptoms to characterize the US features of this common manifestation and to assess whether these findings could help differentiate Löfgren’s syndrome (LS) from other conditions.

Materials and Methods. Thirteen consecutive patients with acute onset of EN and mono- or bilateral ankle involvement (arthralgia/arthritis/swelling) were recruited at a single rheumatologic centre. All patients underwent specific diagnostic investigations aimed at identifying the cause of EN, separating those cases in which it was a manifestation of LS from those in which it was secondary to other causes (OC). An experienced operator in musculoskeletal US, blinded to the course of the diagnostic work-up, performed US examination of ankles bilaterally, investigating the presence of the following parameters: (a) Joint effusion/synovitis at tibiotalar joint (TT JEP); (b) Tenosynovitis (TS) at anterior (AC), lateral (LC) and medial compartment (MC) level; (c) Soft cutaneous tissue inflammation (SCTI) around the ankle. All parameters were initially scored according to OMERACT definition, both for grey scale (GS) and Power Doppler (PD), except for SCTI which were scored according to GLOUDAS definition. US features were classified as positive if their OMERACT parameters were GS>=2 and PD>=1 and if GLOUDAS GS and PD SCTI were >=1. Chi-square test was performed to assess the association between patients diagnosed with LS and US findings.

Results. At the end of the diagnostic workup, 8 patients were diagnosed with LS; whereas the remaining patients received diagnosis of mediastinal lymphoma, Sweet's syndrome during pregnancy, EN secondary to Chron's disease, reactive manifestation during M. homini infectiction and one case remained idiopathic. Demographic and clinical details of the recruited cohort are reported in table 1. Mean time of the US examination was 5 minutes. The prevalence and comparison of US findings in the whole group, in LS group and in OC group are shown in table 2. In particular, within the comparison of LS vs OC, we found a higher prevalence of bilateral positive SCTI, MC and LC compartment TS in the LS group. At statystical analysis, bilateral TS of MC and bilateral SCTI were associated with LS (p<0.095 and p<0.001 respectively) while no statystical difference was found for TT JEP between the two groups.

Conclusions. Despite widely considered as arthritis for its clinical appareance, our study shows how the typical ankle involvement in LS is characterised by a periarticular inflammation, tipically involving soft tissue and tendons without involving talo-navicular joint. Identifying those features with a rapid US ankles assessment in patients with new diagnosis of EN, may raise suspicion for LS, addressing diagnostic and therapeutic workup even during a outpatient visit.