This study is for people with a lung disease called pulmonary Mycobacterium avium complex (MAC) disease. MAC is a type of bacteria that can cause lung problems, especially in people over 60. The goal is to see if taking 2 antibiotics instead of 3 can make treatment easier without losing effectiveness. The study compares azithromycin and ethambutol (2-drug therapy) with azithromycin, ethambutol, and rifampin (3-drug therapy). It will last 18-24 months, the usual time it takes to treat this disease. Participants will have regular check-ups to monitor side effects like nausea and fatigue. Serious side effects may include eye and hearing problems. Only people over 18 who can provide consent and meet specific health criteria can join. Those with certain conditions like cystic fibrosis or HIV can't participate.

• Study lasts 18-24 months with regular visits.
• Tests if 2-drug therapy is as good as 3-drug therapy.
• Tracks side effects and treatment results.