Purine Synthesis Inhibitors, 6-thioguanine and Azathioprine: Forgotten Treatment Options in Psoriasis and Psoriatic Arthritis

Abstract

Background The thiopurine drugs azathioprine and 6-thioguanine have been shown to induce significant clinical improvement in patients with moderate to severe psoriasis and/or psoriatic arthritis. Objective The aim of this paper is to present a comprehensive review of the available literature concerning the off-label role of thiopurine drugs in the treatment of psoriasis and psoriatic arthritis. Methods Studies published with English abstracts between 1960 and 2008 identified in MEDLINE and PubMed with the keywords purine synthesis inhibitors, thiopurine, 6-thioguanine, azathioprine, psoriasis and psoriatic arthritis were reviewed. Results Although 6-thioguanine and azathioprine have shown significant efficacy, their side effect profiles have discouraged their use for moderate to severe psoriasis. Conclusion For treatment of psoriasis and psoriatic arthritis, purine synthesis inhibitors should not be forgotten. They represent an entirely different option and provide an alternative therapy, especially for difficult cases.