Symptoms of rare diseases often creep up quietly, rather than arriving with the brutal shock of a sudden lifestyle upheaval. The change is gradual—unyielding and relentless in its impact. One moment, I was darting around the globe, making things happen with agility and speed; the next, it felt as though someone had chained a 1 kg weight to my ankle..

How two sisters mastered the technology of critical care to help their mother live with ALS. Darji was a profoundly devout man. His piety...