Subsequently, we have demonstrated that high synovial lipid peroxidation positively correlated with clinical disease activity scores, and we have reported reduced 4-HNE levels in patients with RA who responded to tumour necrosis factor (TNF) blocking therapy corresponding with a significant increase in partial oxygen pressure in synovial tissue, indicating a reduction in synovial oxidative stress as the joint tissue becomes less hypoxic [23]. The gene discussed is TNF; the disease is rheumatoid arthritis.