A synovial pathergy reaction leading to a pseudo-septic arthritis and a diagnosis of Behçet's disease

Synovial Tissue Sampling in Rheumatological Practice-Past Developments and Future Perspectives

Synovial biopsies are performed in routine clinical care in order to refine diagnosis as well as within a research setting. Progress in the development of minimally invasive synovial sampling methods in the last century has accelerated and facilitated novel insights into disease pathogenesis. This review discusses the development of synovial biopsy techniques as well as examining the three currently most commonly used approaches: arthroscopic, blind needle biopsy and ultrasound guided approaches. It also highlights major research advances driven through synovial research and considers future developments.

Pseudoseptic arthritis resulting in joint destruction

Pseudoseptic arthritis is an increasingly recognised entity. It is an inflammatory arthritis that mimics septic arthritis; however, Gram stain and cultures are persistently negative. It is a diagnosis of exclusion. We present the first case, to date, in which pseudoseptic arthritis led to such severe joint degeneration that joint replacement surgery was required. A 54-year-old truck driver with rheumatoid arthritis, on immunosuppressive therapy, presented with acute onset severe left hip pain. He was given a clinical diagnosis of septic arthritis and treated with two prolonged courses of antibiotics despite persistently negative synovial fluid cultures. He experienced progressive joint destruction necessitating a two-stage total hip replacement. A retrospective diagnosis of pseudoseptic arthritis was made. This case demonstrates the difficulties inherent in differentiating between septic and pseudoseptic arthritis. This case also highlights the importance of accurate diagnosis and treatment for pseudoseptic arthritis to avoid accelerated joint destruction.

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.

Distinct synovial immunopathology in Behçet disease and psoriatic arthritis

INTRODUCTION

The aim of the study was to investigate synovial immunopathology differences between early Behçet disease (BD) and psoriatic arthritis (PsA).

METHODS

Needle arthroscopy of an inflamed knee joint was performed in patients with early untreated BD (n = 8) and PsA (n = 9). Synovial fluid (SF) was collected for cytokines, perforin, and granzyme analysis. Eight synovial biopsies per patient were obtained for immunohistochemical analysis of the cellular infiltrate (T cells, natural killer cells, macrophages, B cells, plasma cells, mast cells, and neutrophils), blood vessels as well as expression of perforin and granzyme. The stained slides were evaluated by digital image analysis.

RESULTS

The global degree of synovial inflammation was similar in the two types of arthritis. In the analysis of the innate immune cell infiltration, there was a striking neutrophilic inflammation in BD synovitis whereas PsA displayed significantly higher numbers of cells positive for c-kit, a marker of mast cells. As for lymphocytes, CD3+ T cells, but neither CD20+ B cells nor CD138+ plasma cells, were significantly increased in BD versus PsA. Further analysis of the T-lymphocyte population showed no clear shift in CD4/CD8 ratio or Th1/Th2/Th17 profile. The SF levels of perforin, an effector molecule of cytotoxic cells, displayed a significant four- to fivefold increase in BD.

CONCLUSIONS

This systematic comparative analysis of early untreated synovitis identifies neutrophils and T lymphocytes as important infiltrating cell populations in BD. Increased levels of perforin in BD suggest the relevance of cytotoxicity in this disease.