There will be a total of 9 study visits until Week 26: screening, study entry, Week 2, and every 4 weeks thereafter. Each study visit will include a physical exam, vital signs measurement, medical and medication history, a review of the disease activity log and adverse events experienced since the last visit, skin assessments, and blood collection; patients will also be asked to complete a tuberculosis (TB) questionnaire. Patients will be asked to complete quality of life questionnaires at study entry and Weeks 10, 18, and 26. Skin biopsies of unaffected skin will be done at study entry and Weeks 10, 18, and 26; if patients have PV-associated lesions, additional skin biopsies of affected skin will be done at study entry and Week 18.