Photographs of an American holding a hunger strike in Cairo to protest his imprisonment without charges show him badly bruised and gravely ill, raising alarms about his deteriorating health and possible abuse.

On Tuesday the family of the American, Mohamed Soltan, released six photographs taken in prison that showed him unconscious with blood running out of his mouth, sores on his lips and gums, and large bruises on his hands and arms.

Mr. Soltan, 27, is one of several thousand political prisoners arrested in Egypt during a crackdown on dissent after the ouster of President Mohamed Morsi of the Muslim Brotherhood in 2013. He is also a dual citizen of the United States and Egypt who attended high school and college in the Midwest.

In a recent letter to the family that was provided to The New York Times, American diplomats working on the case warn that his hunger strike “has done and continues to do severe, in some cases irreparable, damage to his body” and “is a significant threat to his life.”