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The list of so called ‘disease modifying agents’ in rheumatoid arthritis now includes methotrexate and cyclosporin A. The efficacy of certain speculative treatments in the rheumatic diseases including antibody based therapies such as anti-tumour necrosis factor1 and anti-ICAM,2 cytokine toxic fusion proteins,3 oral administration of antigens,4 stem cell therapy,5 and cytokine receptor antagonists6 are being investigated. After the reported success of extracorporeal photochemotherapy (ECP) in systemically disseminated cutaneous T cell lymphoma7 in 1987 its benefits are also being explored in rheumatological conditions.
Technique of ECP
Two hours after oral methoxypsoralen, blood is removed from the patient, exposed to ultraviolet A light at room temperature, and then reinfused. This procedure can either be done as a continuous flow or by concentrating the lymphocytes and reinfusing as a bolus, and is usually performed on two consecutive days each month. In the initial group of 37 patients with therapy resistant cutaneous T cell lymphoma 27 improved with ECP, and over the past 10 years ECP has been adopted increasingly for this condition.
Mechanisms of ECP
Methoxypsoralen is a photoreactive agent that is temporarily transformed into its active form on exposure to ultraviolet A light before reverting in a fraction of a second to its inactive state. While ultraviolet A activated psoralens have a direct effect on intracellular DNA8 leading to cell death, this alone is unlikely to account for the …