Study refutes theory that genetic diseases occur earlier in children than in their parents

Nature : Genetic prion diseases, such as Creutzfeldt–Jakob disease , occur when inherited genetic mutations cause a person’s prion proteins to fold incorrectly. So far such diseases have proven to be untreatable and fatal. Last year a paper in the journal PLOS ONE reported that successive generations die younger of such inherited diseases. That finding has now been refuted by a computational scientist at Massachusetts General Hospital in Boston. Eric Minikel was inspired to look more closely at the issue because his wife carries the genetic mutation for fatal familial insomnia, another genetic prion disease. He persuaded the four leading prion centers in the world to check their data for sampling bias . He reasoned that because such genetic mutations have only been discovered relatively recently, in1989, most of the data collected would cover just two generations—parents and their children. Over such a short time period, if both parents and children developed the same disease, the parents would have had to be older at age of onset. However, when more information on the life spans of multiple generations of a family was available, there was no indication that the age of onset of such diseases was decreasing.