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.
The fact that your husband is older now than any affected family member at the time of diagnosis and has no symptoms is definitely a good sign that he may not develop either of these diseases. Early symptoms can be subtle, and an expert such as a neurologist who specializes in movement disorders could make the diagnosis months or years before symptoms become noticeable to you or your husband, although I am sure you are more adept at noticing them.
There are genetic tests available for many of the identified familial genetic variations; however, their interpretation is difficult. Further, since we don’t have therapies that can stop or slow down the progression of Parkinson’s disease, I do not recommend genetic testing for Parkinson’s disease.
