Each study subject will receive either 2 infusions of rituximab (each 1000 mg; given 2 weeks apart) or 2 intravenous infusions of saline. Glucocorticoids (methylprednisolone 100 mg) or saline will also be administered IV as premedication to the rituximab and placebo arm respectively, in a blinded fashion but matching the randomization, to decrease the rate of infusion-associated reactions. All antihypertensive medications will be held for the 12 hours prior to and during the infusion. Patients will return 2 weeks after the first intravenous infusion in order to receive the second infusion.