This project aims to study systemic sclerosis and find a serum marker of its cutaneous involvement.

Systemic sclerosis (SSc) is a rare immune disease that is part of connectivitis and is characterized by fibrosis and vasculopathy. Multiple visceral lesions involving these two processes make up the severity of this disease. Its dermatological involvement is a fundamental clinical element.

Systemic sclerosis is mainly divided into two subtypes, depending on the extent of dermatological involvement: limited and diffuse systemic sclerosis. These also differ in certain autoantibody profiles and clinical features. Nevertheless, it is still necessary to determine certain criteria, markers, making it possible to distinguish at an early stage the presence of limited or diffuse systemic sclerosis. The latter being characterized by more severe organic and cutaneous involvement and excess mortality. This would allow for more aggressive management from the outset at an early onset of the disease.

In general, it is known that this pathology is characterized by dysfunction of endothelial cells (EC) and fibroblasts as well as autoimmunity. Many mediators contribute to the fibroblast activation observed in SSc. However, transforming growth factor beta (TGFβ) is considered to be the central regulatory factor of fibrosis processes.

It is also known that endothelial cells interact with mast cells through the production of Stem Cell Factor (SCF) to induce their proliferation and differentiation. The damaged skin tissues in systemic sclerosis are infiltrated in particular by mast cell cells which produce TGFβ.

The team of Kihira et al (1998) demonstrated the presence of a high level of SCF in the serum of patients with systemic sclerosis.

Few studies explore this possible production pathway of TGFβ in systemic sclerosis via SCF assay.

This study will allow the investigators to:

• study this possible route of fibrosis through the dosage of SCF in the serum of patients suffering from systemic sclerosis
• describe SCF as a possible biomarker of skin involvement by hypothesizing that the dosage of SCF will be higher in patients with diffuse scleroderma compared to those with limited scleroderma

Inclusion Criteria:

• Patients followed regularly at CHU Brugmann in Rheumatology/Dermatology for limited or diffuse systemic sclerosis in accordance with the ACR/EULAR 2013 criteria.
• Control patients recruited among patients followed for mechanical pathology in rheumatology

Exclusion Criteria:

• Patients with comorbidities of hematological diseases, asthma or severe chronic renal failure (GFR < 30)

Patients followed regularly at CHU Brugmann in Rheumatology/Dermatology for limited or diffuse systemic sclerosis in accordance with the ACR/EULAR 2013 criteria.