What is the difference between progresive multifocal leukoencephilopathy (pml) and reversible posterior leukoencephalopathy syndrome (rpls)?

Different problems. Pml is a viral disease affecting the brain and occurs in patients with compromised immune systems such as those with aids, transplants, cancer, etc. Rpls is a reversible syndrome of headaches, seizures, confusion, and other symptoms due to medications, high blood pressure, etc. And improves upon treatment of the underlying disorder.