OBJECTIVES Behçet's disease (BD) is a chronic inflammatory disease of unknown etiology, characterised by recurrent oral and genital ulcers, skin lesions, uveitis, and arthritis. It is regarded as vasculitis and anti-endothelial cell antibodies (AECA) are found in patients with BD. One of the endothelial cell antibodies was reported to recognise alpha-enolase. This study aimed to investigate expression of alpha-enolase in the surface of peripheral blood cells and serum anti-alpha-enolase antibody (AEA), and their association with clinical manifestations or disease activity of BD.

METHODS Cell surface alpha-enolase expression was examined from several cell types of peripheral blood, including lymphocytes, monocytes, and neutrophils using flow cytometry in patients with BD and healthy controls (HCs). IgG AEA levels were measured by enzyme-linked immunosorbent assay (ELISA) in sera from 110 patients with BD, and age/sex matched 110 HCs. Association of alpha-enolase or AEA with clinical manifestation was analysed.

RESULTS The frequency of surface alpha-enolase-expressing cells was increased in BD in lymphocytes and monocytes. Serum AEA levels were in- creased in BD patients (median [IQR], 0.360 [0.268-0.482], p < 0.0001), particularly with mucocutaneous involvement (0.367 [0.273-0.490], p < 0.0001) compared to HCs (0.274 [0.231-0.357]). The levels of AEA were correlated with the number of oral ulcer, ESR, and CRP. There was no association between serum levels of AEA and other clinical manifestations.

CONCLUSIONS Serum AEA was increased in BD patients and correlated with oral ulcer, ESR and CRP.