The goal of this observational study is to elucidate the role of serum amyloid A (SAA) in the diagnosis and follow-up of sarcoidosis, including its prognostic value. The main questions it aims to answer are:

• Whether, at the time of diagnosis, SAA is in correlation with other serum markers of granulomatous inflammation, interstitial disease and pulmonary fibrosis, lung function and radiologic characteristics of intrathoracic sarcoidosis,
• Whether increased serum concentrations of SAA at the time of diagnosis act as a prognostic marker of progressive granulomatous inflammation and pulmonary interstitial disease.

Patients will undergo standard diagnostic procedures for intrathoracic sarcoidosis, according to WASOG (World association of sarcoidosis and other granulomatous disorders) criteria. Two additional vials of blood will be taken at diagnosis and one vial at follow-up for serum processing and biomarker analysis.

Healthy blood donors will represent our group of healthy controls.

Inclusion Criteria:

• Above 18 years of age
• Enrolled immediately after the first diagnostic workup and before any treatment was initiated.

Exclusion Criteria:

• Individuals with granulomatous disease that could not be unequivocally diagnosed as sarcoidosis were excluded, as well as patients with possible confounding other known systemic inflammatory illnesses, acute infection, patients on immunosuppressive drugs or immunotherapy and patients with active cancer.

• All patients comply with the accepted European Respiratory Society/ World Association of Sarcoidosis and Other Granulomatous disease (ERS/WASOG) guidelines for the diagnosis of sarcoidosis and have undergone complete functional and radiological assessment, including spirometry.
• Histological confirmation of non-caseating granulomas in thoracic lymph nodes and lung parenchyma has been obtained by flexible bronchoscopy, as well as bronchoalveolar lavage (BAL) fluid for the determination of BAL CD4+/CD8+ ratio.