CAIRO — MOHAMED SOLTAN knew he had one thing going for him when the Egyptian police came to his door: He was a United States citizen, raised primarily in Ohio.

It did not mean much in the moment. The police had come looking for his father, Salah Soltan, an outspoken member of the Muslim Brotherhood. But when they found only Mohamed Soltan and three friends, the police arrested them instead, along with tens of thousands of others thought to be Islamists or liberal dissidents who were rounded up after the military takeover here two years ago.

But his American citizenship helped embolden Mr. Soltan, then 25, to carry out a hunger strike for 16 of his 21 months in prison, shedding more than 160 of the original 272 pounds on his 5-foot-11-inch frame and risking organ failure in the belief that the United States government might come to his aid.

His citizenship brought special torments from jailers seeking to break him, like when he was locked in a room overnight with a dying man screaming in pain and then left alone with the corpse for most of the next day.