The studies presented in the PhD thesis of Nienke Kleinrensink (UMC Utrecht) show – with the help of medical imaging - that subclinical disease is common at the site where tendons and ligaments attach to the bone in patients with psoriasis and psoriatic arthritis. In addition, the inflammatory reaction in psoriatic arthritis may also involve non-musculoskeletal organs such as the arterial wall.

Psoriatic arthritis (PsA) is a chronic inflammatory musculoskeletal disease, with diverse clinical manifestations including psoriasis of the skin or nails, in combination with peripheral arthritis, dactylitis (swelling of an entire finger or toe), enthesitis (inflammation at the site where tendons/ligaments attach to the bone) or axial disease. PsA is part of a group of rheumatic conditions that are referred to as 'spondylarthritis'. With the use of imaging techniques such as x-ray, magnetic resonance imaging (MRI) and, in experimental settings, positron emission tomography/computed tomography (PET/CT), healthcare providers can capture the diverse (sub)clinical disease manifestations of PsA, to advance the understanding of disease pathogenesis, monitor disease activity or to predict treatment response. In her PhD thesis, Nienke Kleinrensink, MD (Department of Rheumatology & Clinical immunology and Department of Radiology, UMC Utrecht) investigated imaging techniques to improve monitoring of disease activity in patients with early PsA, and to gain further insights in vascular inflammation in psoriatic disease.

Key findings

•  Abnormalities in the Heel Enthesitis MRI Scoring System (HEMRIS) were common in clinically unaffected plantar fascia and Achilles tendons of psoriasis and spondyloartritis patients;
• In Achilles tendons of spondyloartritis patients with clinical enthesitis, the HEMRIS score for structural damage was elevated;
• In psoriasis and spondyloartritis patients, there was a weak correlation between total and structural damage HEMRIS scores and local metabolic activity on PET/CT at the Achilles tendon;
• During 1-year follow-up, only minimal changes in the HEMRIS were observed in psoriasis and spondyloartritis patients. Changes in the HEMRIS scores were not associated with changes in clinical disease activity;
• Both psoriasis and PsA are associated with increased arterial inflammation on PET/CT;
• There is insufficient evidence for a beneficial effect of treatment with 'biologicals' on arterial inflammation in psoriasis patients.

Although many further steps are needed, the works presented in this thesis show – with the help of medical imaging techniques - that subclinical disease is common at enthesis of psoriasis and spondyloarthritis patients and that the inflammatory reaction in PsA may also involve non-musculoskeletal organs such as the arterial wall. Finally, with the TOFA predict study, which is currently recruiting patients and of which the study protocol is described in this thesis, investigators at Dutch hospitals will aim to deliver evidence-based imaging predictors of treatment response in patients with PsA and learn more on the relevance of subclinical findings on MRI and PET/CT.

PhD defense

Nienke Josephine Kleinrensink, MD (1989, Hamburg, Germany) defended her PhD thesis on June 18, 2024 at Utrecht University. The title of her thesis was “Imaging insights into the diverse manifestations of psoriatic arthritis”. Supervisors were prof. Pim de Jong, MD PhD (Department of Radiology, UMC Utrecht) and prof. Floris Lafeber, PhD (Department of Rheumatology & Klinische Immunology, UMC Utrecht). Co-supervisors were Wouter Foppen, MD PhD (Department of Radiology, UMC Utrecht) and Julia Spierings, MD PhD (Department of rheumatology & Clinical Immunology, UMC Utrecht). Nienke works as a resident in rheumatology at the St. Antonius Hospital and at UMC Utrecht.