Light and electron microscopic features of synovium in patients with psoriatic arthritis

Few ultrastructural studies have been reported in psoriatic arthritis (PsA). The authors report a series of synovial biopsies with emphasis on patients with early disease to look for distinctive light (LM) and electron microscopic (EM) features of possible importance.

The authors examined synovial biopsies obtained primarily by needle biopsy from 13 PsA patients using LM and/or EM. Sections from 12 patients were evaluated by LM for vascularity, synovial lining thickness, fibrin deposition, and inflammation via a semi-quantitative scale. Nine EM specimens were descriptively analyzed. Clinical, synovial fluid (SF), and radiographic characteristics were recorded.

Patients were mostly male, with mean disease duration before biopsy of 2.19 ± 2.60 years; 7 patients had arthritis for less than 1 year. All patients had peripheral arthritis, 2 had axial involvement. SFs disclosed predominance of polymorphonuclear leukocytes. LM demonstrated proliferation of synovial lining cells, lymphocyte and plasma cell infiltration, as well as dramatic clusters of small vessels in the superficial synovium. EMs showed more detailed vascular changes, including small, subendothelial, electron-dense deposits and scattered microparticles in vessel lumens and walls.

Prominent vascularity is confirmed as an important feature of some PsA. Vascular changes and other features, including the first EM demonstration of microparticles in PsA (identified as potent factors in other inflammatory joint diseases), are potential targets for therapy.