TREATMENT Eligible patients will be randomized to receive either 18 months of Rituximab and Azathioprine (20 patients) or placebo (20 patients). Rituximab will be administered intravenously (IV) weekly for four consecutive weeks at enrollment and months 6 and 12. IV placebo will be administered on the same schedule as Rituximab. Azathioprine or oral placebo will be administered by mouth daily for 18 months.