In February 2005, an HIV patient in an unusually difficult situation walked into a neuroimmunology clinic at Johns Hopkins University, where he was seen by the specialist Avindra Nath. The patient had not only immune deficiency resulting from HIV infection, but amyotrophic lateral sclerosis (ALS) as well, and the neurodegenerative disease was causing his condition to deteriorate rapidly. For several months, the patient had noticed his hands and feet becoming increasingly sore and weak, making tasks such as eating with utensils or opening a window all but impossible. When Nath saw him, the 29-year-old had difficulty climbing stairs and couldn’t get up from a seated position on the floor without assistance.
The patient was initially reluctant to take a combination ...