A drug for rheumatoid arthritis can relieve the suffering of patients with moderate to severe psoriasis for a year, researchers said on Friday.They found that infliximab, which is marketed under the name Remicade by Johnson & Johnson in the United States and by Schering-Plough Corp in other markets, improved symptoms of the chronic skin condition that affects 2 percent of the population in western countries."This is the first study to show that the very rapid and dramatic improvement that you see with psoriasis can, in the majority of patients, be maintained over at least the medium term -- over the course of a year,” said Professor Christopher Griffiths, of the University of Manchester in England.Previous trials have only looked into the impact of the drug on psoriasis over a short period of about 12 weeks.The study published in The Lancet medical journal also showed patients saw a significant improvement in one of the most disturbing features of psoriasis: nail disease.