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Parkinson's Disease

Patterns

11/14/1999

Question:

If you have Parkinson`s coming in from your mom and dad`s family,and your their only son could you getit????

Answer:

The role of genetics in PD is somewhat controversial. There clearly are familial forms of Parkinson`s disease, e.g. one form associated with the alpha-synuclein gene. However a recent study on identical and fraternal twins showed a similar incidence in twins of both kinds when the other twin had PD. One would expect that in identical twins with identical DNA there would be a greater incidence of PD in both twins. However, it is possible that a longer follow-up period would have revealed a difference in rates.

There are other neurological diseases such as Huntington`s Disease with an autosomal dominant pattern of inheritance. In such a case, presence of one parent with the disease means that every child has a 50% chance of developing the disease. Such a pattern is unlikely in PD. Even in familial cases which may have autosomal dominant inheritance one encounters "poor penetrance". This means that even if the genetic structure favors development of disease, not everyone with this genetic make-up will actually end up with the disease.

If the above explanation is not complicated enough, one has to also consider other factors. First, that Parkinson`s disease may be polygenic, meaning that more than one abnormal gene may be necessary to develop the disease and second that there may be a gene-environment interaction. That is, even though you have an abnormal gene, you would need to be exposed to the same kind an amount of environmental toxins as your parents to develop disease. We do not yet know the specific toxin or toxins responsible. A recent NIH request for applications is geared towards promoting research into gene-environment interactions.

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Response by:

Arif Dalvi, MD
Assistant Professor
College of Medicine
University of Cincinnati