Anticipation in hereditary disease: the history of a biomedical concept.

In the mid-nineteenth century, it was commonly believed that hereditary disease struck at the same time in succeeding generations, except for those cases in which it appeared at an earlier age. This exception to the rule was the precursor for the concept of anticipation in hereditary disease, a pattern of inheritance where a hereditary illness strikes earlier and often more severely in succeeding generations. Anticipation underwent cycles of acceptance and rejection over the course of the twentieth century and the ways in which this concept was received reveal complex interactions between science, medicine, and society.