This study aims to measure a blood protein called fibroblast activation protein (FAP), which is linked to tissue scarring and inflammation. A small blood sample will be taken from participants (RA , SSc patients and healthy people ), and the FAP level will be measured and compared with routine clinical examinations, imaging studies, and lung function tests.

The purpose of this study is to improve understanding of disease activity and lung involvement in these conditions and to explore whether FAP could be useful as a blood marker for future patients. Participation in this study will not change the participant's usual medical care.

Inclusion Criteria:

• Age ≥18 years. Confirmed diagnosis of RA (ACR/EULAR) or SSc (ACR/EULAR).
• Ability and willingness to provide informed consent. Cooperative patient able to answer questions.

Exclusion Criteria:

• Patients under 18 years' old
• Active cancer or history of cancer within 5 years.
• Other major fibrotic systemic disease that could confound circulating FAP levels.
• Acute infection at time of sampling.
• Pregnancy or breastfeeding.
• Other autoimmune diseases

The study population will include adult patients diagnosed with rheumatoid arthritis (RA) or systemic sclerosis (SSc). Participants will be recruited consecutively from the Rheumatology and Rehabilitation outpatient clinics and inpatient units of the study center.

The sample will consist of three parallel groups:

Patients with rheumatoid arthritis diagnosed according to the 2010 ACR/EULAR classification criteria.

Patients with systemic sclerosis diagnosed according to the 2013 ACR/EULAR classification criteria.

Healthy population who don't have any autoimmune disease.