Macroscopic features of knee synovitis in early untreated Behçet disease and psoriatic arthritis

In a previous study, we found that synovial immunopathology differs between Behçet disease (BD) and psoriatic arthritis (PsA). The objective of this study is to describe the macroscopic features of early untreated knee synovitis in BD and PsA. Fourteen consecutive patients with active early knee synovitis (seven BD and seven PsA) undergoing rheumatologic arthroscopy were assessed. The following macroscopic synovial features were evaluated and scored by analyzing the video recordings of each procedure: capillary hyperaemia, morphology of synovitis, vascular pattern, fibrinoid membranes, and topographic distribution of these features. Video-recording of 35 early untreated arthritis patients with different diagnoses were also studied looking for BD-like macroscopic features. Six out of seven BD patients had extensive fibrinoid membranes and large areas of erythematous synovitis without villi or a distinctive vascular pattern, while PsA patients had diffuse erythematous villous synovitis with a tortuous vascular morphology. None of the 35 patients with early untreated arthritis exhibited all the characteristic features of BD synovitis. This exploratory study shows some distinctive features between BD and PsA knee synovitis that confirm macroscopic differences in patients with previously reported immunopathological differences.