In familial Mediterranean fever, soluble TREM-1 plasma level is higher in case of amyloidosis

We aimed to explore triggering receptor expressed on myeloid cells-1 (TREM-1) activation in familial Mediterranean fever (FMF), the most frequent monogenic auto-inflammatory disease, through the measurement of its serum soluble form, named sTREM-1. Blood samples from patients with FMF according to Livneh criteria followed in the French FMF national center and carrying two pathogenic MEFV mutations were collected. Serum level of sTREM-1 was assessed using ELISA. Demographic data, presence of FMF attack, association with histologically proven AA amyloidosis, and blood levels of C-reactive protein (CRP), serum amyloid A (SAA) protein, and creatinine were collected. TREM-1 was available in 56 patients (33.9% male, mean age 43 yr); AA amyloidosis was associated in six patients (19.6% in FMF). Mean sTREM-1 level did not differ significantly between patients having an attack or not and there was also no significant correlation between the level of sTREM-1 and CRP and SAA protein. However, the mean rate of sTREM-1 was significantly higher among FMF patients with AA amyloidosis versus without, though the concomitant SAA protein level was normal. Serum level of sTREM-1 was higher in patients with amyloidosis even though the concomitant SAA protein level was normal. sTREM-1 plasma levels could be an accurate tool to specifically identify FMF patients with amyloidosis.