Anatomical pattern of entheseal and synovial fibroblast activation in patients with psoriasis and its risk of developing psoriatic arthritis.

OBJECTIVES: To assess the presence and anatomical distribution of activated fibroblasts in the joints and entheses of patients with psoriasis with arthralgia and to test how fibroblast activation visualised by 68gallium-labelled fibroblast activation protein inhibitor-04 (68Ga-FAPI-04)-positron emission tomography (PET)/CT correlates with clinical tenderness, musculoskeletal ultrasound findings and progression to psoriatic arthritis (PsA). METHODS: We conducted a prospective cohort study in patients with psoriasis and arthralgia who underwent clinical and ultrasound evaluation and whole-body PET/CT imaging with 68Ga-FAPI-04. 68Ga-FAPI-04 uptake at synovial and entheseal sites was assessed by maximal standardised uptake values (SUVmax) and PET/CT Joint Index (JI); logistic regression models were used to investigate its correlation with clinical and ultrasound findings. Survival analyses were performed on patients with at least 6 months of follow-up. RESULTS: 36 patients with psoriasis were enrolled. 68Ga-FAPI-04 uptake was found in 318 (7.9%) joints and 369 (7.3%) entheses in 29 (80.6%) participants, with a mean SUVmax (SD) of 3.2 (1.8) for joints and 2.9 (1.6) for entheses. Large joints and the lower limbs were predominantly affected. A significant positive relationship was found between 68Ga-FAPI-04-PET/CT signal intensity and the 68 tender joint count (SUVmax: p<0.001; PET/CT-JI: p<0.001) and tender entheses count (SUVmax: p<0.001; PET/CT-JI: p=0.002). No correlations were found with ultrasound findings (SUVmax: p=0.969; PET/CT-JI: p=0.720). Patients with relevant synovio-entheseal 68Ga-FAPI-04 uptake showed a statistically significant higher risk of developing PsA (p=0.02), independent of ultrasound findings. CONCLUSIONS: Patients with psoriasis presenting with arthralgia show localised signs of resident tissue activation in joints and entheses, which are associated with higher risk of developing PsA.

Unveiling metabolic similarities of entheses in psoriasis and psoriatic arthritis patients using non-invasive in vivo imaging - results from the MAPSA study.

OBJECTIVES: To assess and compare molecular tissue changes at the entheses in patients with psoriasis (PsO), psoriatic arthritis (PsA), and healthy controls (HC) in vivo using multispectral optoacoustic tomography (MSOT) and to describe their relationship with clinical and ultrasound findings of enthesitis. METHODS: A cross-sectional study (MAPSA) in bDMARD-naïve PsA and PsO patients and HC was performed. Participants underwent clinical, ultrasonographic and MSOT examination of six entheses (lateral humeral epicondyle, distal patellar tendon attachment, Achilles tendon attachment). MSOT-measured haemoglobin (Hb), oxygen saturation (SO2), collagen, and lipid levels were quantified and mean differences between groups were calculated using linear mixed-effects models. MSOT-measured analytes were compared between entheses with and without clinical and ultrasound anomalies. RESULTS: Ninety participants were included (30 PsO, 30 PsA, 30 HC), 540 entheses were clinically assessed, and 540 ultrasound and 830 MSOT scans were obtained. Both PsA and PsO patients showed increased oxygenated Hb (PsA: p=0.003; PsO: p=0.054) and SO2 (PsA: p<0.001; Pso: p=0.001) levels and decreased collagen signals (PsA: p<0.001; PsO: <0.001) compared to HC, with more pronounced changes in PsA. Significantly lower collagen levels (p=0.01) and increased lipids (p=0.03) were recorded in tender entheses compared to non-tender ones. Erosions and enthesophytes on ultrasound were associated with significant differences in SO2 (p=0.014) and lipid signals (p=0.020), respectively. CONCLUSIONS: PsA and PsO patients exhibit an analogous metabolic pattern at the entheses that is exacerbated in the presence of inflammation. These findings support the notion of a psoriatic disease spectrum characterized by common immuno-metabolic tissue changes.

Anti-interleukin-6 receptor antibody for the treatment of remitting seronegative symmetrical synovitis with pitting oedema: a new outlook?

We present the case of an elderly man with a small-joint polyarthritis, accompanied by pitting oedema, involving hands and feet, raising clinical suspicion of remitting seronegative symmetrical synovitis with pitting oedema (RS3PE). Treatment with corticosteroids was initiated with significant improvement, but unacceptable iatrogeny ensued, and tapering was not possible without disease flare-up. A trial of tocilizumab allowed disease activity control, slow weaning of corticosteroids and, ultimately, its suspension. RS3PE is a rare rheumatological entity, initially thought to be a variant of rheumatoid arthritis (RA), with shared traits with polymyalgia rheumatica (PMR), and other seronegative spondyloarthropathies, thereby implying a shared pathophysiological background. Elevated levels of interleukin 6 (IL-6) are found in patients with RA, have shown to mirror disease activity in PMR and have also been described in the serum and synovial fluid of patients with RS3PE. Tocilizumab, an anti-IL-6 receptor antibody, shows auspicious results in several other rare rheumatic diseases other than RA.

Metabolic and molecular imaging in inflammatory arthritis.

It is known that metabolic shifts and tissue remodelling precede the development of visible inflammation and structural organ damage in inflammatory rheumatic diseases such as the inflammatory arthritides. As such, visualising and measuring metabolic tissue activity could be useful to identify biomarkers of disease activity already in a very early phase. Recent advances in imaging have led to the development of so-called 'metabolic imaging' tools that can detect these changes in metabolism in an increasingly accurate manner and non-invasively.Nuclear imaging techniques such as 18F-D-glucose and fibroblast activation protein inhibitor-labelled positron emission tomography are increasingly used and have yielded impressing results in the visualisation (including whole-body staging) of inflammatory changes in both early and established arthritis. Furthermore, optical imaging-based bedside techniques such as multispectral optoacoustic tomography and fluorescence optical imaging are advancing our understanding of arthritis by identifying intra-articular metabolic changes that correlate with the onset of inflammation with high precision and without the need of ionising radiation.Metabolic imaging holds great potential for improving the management of patients with inflammatory arthritis by contributing to early disease interception and improving diagnostic accuracy, thereby paving the way for a more personalised approach to therapy strategies including preventive strategies. In this narrative review, we discuss state-of-the-art metabolic imaging methods used in the assessment of arthritis and inflammation, and we advocate for more extensive research endeavours to elucidate their full field of application in rheumatology.