This study evaluates the potential of positron emission tomography (PET)/computed tomography (CT) imaging to monitor disease activity in patients with systemic sclerosis (SSc). PET/CT imaging will focus on two pathological features of SSc, i.e. metabolic activity evaluated by glucose analog 18F-FDG, and expression of inflammation-inducible vascular adhesion protein 1 (VAP-1) evaluated by 68Ga-DOTA-Siglec-9 tracer.

In patients with systemic sclerosis (SSc), the quantitative assessment of disease activity is still difficult. Identification of patients who unlikely respond to therapy before or early in a course of the treatment could reduce morbidity and produce cost-savings. This project will evaluate the potential of advanced functional imaging techniques to monitor disease activity. Functional imaging will focus on two pathological features of SSc, i.e. metabolic activity evaluated by glucose analog 18F-FDG positron emission tomography (PET)/computed tomography (CT), and expression of inflammation-inducible vascular adhesion protein 1 (VAP-1) evaluated by new 68Ga-DOTA-Siglec-9 tracer. If successful, the resulting techniques may prove invaluable as tools in the clinical practice and in drug research aiming to find new targets to the treatment of SSc.

Inclusion Criteria:

• Adults with active systemic sclerosis (SSc).
• Onset of SSc (defined as first non-Raynaud symptom) not more than 5 years ago.
• Clinically active disease with proximal nailfold capillary abnormalities detected with videocapillaroscopy and/or raised inflammatory markers (CRP or ESR).

Exclusion Criteria:

• Underage, pregnant, breastfeeding, handicapped or prisoner
• History of or current inflammatory joint disease or autoimmune disease other than SSc.
• History of treatment with, prior to this study, immunosuppressives or disease-modifying anti-rheumatic drugs (DMARDs) such as methotrexate, leflunomide, azathioprine, mycophenolate, cyclophosphamide or biologic agents such as anti-TNF inhibitors, abatacept, or rituximab. Hydroxychloroquine is allowed in the history (≥3 months prior to PET study).
• Intra-articular or parenteral corticosteroids ≤4 weeks prior to PET/CT study.
• Prostanoids or other vasoactive treatments like phosphodiesterase-5 inhibitors or endothelin receptor antagonists ≤4 weeks prior to PET/CT study (the use of calcium channel inhibitors is allowed).

Patients of Turku University Hospital or Kuopio University Hospital with active systemic sclerosis.