Background: Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) is a monocyte and neutrophil receptor functioning in innate immunity. TREM-1 produces proinflammatory cytokines and serves for neutrophil degranulation. TREM-1 activity is well known in the pathogenesis of sepsis; hence it can be also present in autoinflammatory diseases such as the most common monogenic one, Familial Mediterranean Fever (FMF).

Objectives: The objective of this study is to measure soluble TREM-1 (sTREM-1) activity in severe FMF cases complicated with systemic AA-Amyloidosis.

Methods: The cohort of the study includes regularly followed FMF related AA-Amyloidosis patients in a tertiary center outpatient rheumatology clinic. Soluble TREM-1 levels were measured using enzyme-linked immunosorbent assay (ELISA). In addition, demographic data, renal function tests, acute phase reactants, and medical prescription history was also noted and analyzed. None of the FMF diagnosed patients had an attack during the collection of the blood samples.

Results: The patients were categorized into 4 groups: FMF related AA-Amyloidosis patients (A(+) FMF(+)), FMF unrelated AA-Amyloidosis (FMF(-) A(+)), FMF patients without Amyloidosis diagnosis (FMF(+) A (-)), and healthy controls (HC). The mean ages, TREM-1, C - reactive protein (CRP), and Creatinine levels of each group are shown in Table 1 . TREM-1 levels were found to be significantly higher in A(+) FMF(+) group than FMF(+) A (-), and healthy control groups (p= 0.001 and 0.002). Nevertheless, this difference was not found in between A(+) FMF(+) and FMF(-) A(+) (p= 0.447). In addition, the TREM-1 levels of FMF(+) A (-), and healthy control groups were not different (0.532). In A(+) FMF(+) group, 36 patients used colchicine with the mean dose of 1.9±0.8 mg/day, 14 patients used anakinra, and 9 patients used canakinumab. In FMF(+) A (-) group all 20 patients used colchicine with the mean dose of 2.8±0.9 mg/day, 1 patient used anakinra, and 2 patients used canakinumab.

Conclusion: In conclusion, TREM-1 is a proinflammatory marker found significantly high in AA-amyloidosis patients regardless of their FMF diagnosis. TREM-1 may be useful in AA-amyloidosis follow-up and early diagnosis since currently there is a deficit of an early diagnostic marker of amyloidosis. This study is a cross-sectional one so it is hard to reach a conclusion on the effectiveness of TREM-1 during regular FMF follow-up for the secondary prevention of amyloidosis. However, the sensitivity of TREM-1 as a marker cannot be denied in amyloidosis.

Disclosure of Interests: None declared