This article came out yesterday. Very interesting -- I've never heard of this drug--efalizumab for psoriasis. About 46,000 people are on it worldwide. 3 PML cases (2 recent) causing concern. After 3 years on the drug the risk of getting PML is 1:1100. Some doctors are now calling for people to get off it because they don't view that as a risk worth taking.
http://www.medpagetoday.com/MeetingCoverage/SDEF/12849