The treatment component of the study consists of eight weeks of open label N-Acetylcysteine (NAC). All eligible study subjects will be treated with 600mg of NAC twice a day for 2 weeks, then the dose will be increased to 1200mg twice a day for two weeks, and to 1800mg twice a day for 4 weeks. weeks. Subjects will be seen every two weeks during the 8-week study. Efficacy and safety assessments will be performed at each visit.