Dear Dr. Roach: My husband is one of five brothers, all born in the 1940s. Their father died of Parkinson’s disease. Three of the five brothers have been diagnosed with Parkinson’s and/or Lewy body dementia. All the affected brothers developed symptoms in their late 60s or 70s, and my husband is 80 now (the other brother is 75 — neither he nor my husband have any symptoms). What are the chances that the remaining two brothers will be stricken? — L.E.
Answer: Most cases of Parkinson’s disease are sporadic and not familial. However, there are familial cases, and these are more likely when the affected family members are age 50 or less at the time of diagnosis. That being said, I’m compelled to believe there is a family association in your husband’s family, given their history.
I read about many different genes involved in familial Parkinson’s disease, and mutations at some of these genes predispose also to Lewy body disease as well. The mode of inheritance can be recessive, dominant or sex-linked, depending on the gene. Because of the large number of genes, it’s impossible to give precise odds.