Therese Crutcher-Marin’s world was turned upside down when she learned that her fiancé, along with his three sisters, were all at risk for Huntington’s.

Huntington's disease is a devastating inherited condition that produces a combination of neurological, motor, cognitive and psychiatric symptoms. It’s been compared to having Parkinson’s, Alzheimer’s, and ALS all at the same time. There is no cure.

In her new memoir, Watching Their Dance, Crutcher-Marin shares her deeply personal story of marrying into a family at risk for...