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Inherited Disorders and Birth Defects

Preaxial polydactyly

01/30/2008

Question:

My husband has three boys. Two were born with this disorder and the other was not. Is this possible?

Answer:

Polydactyly means extra fingers and/or extra toes. The extra finger or toe can be just partially formed or fully formed. It can be on either the thumb side (preaxial Polydactyly) which seems to be the case for your husband's children or the pinky side (postaxial polydactyly).

Having an extra finger or toe can run in families as an autosomal dominant condition - meaning there is a single gene responsible for the trait. If the polydactyly is caused by a single dominant gene, then anyone who has the gene has a 50-50 chance of passing the gene on to each of his or her children. In your husband's case, if he has the gene, he passed it on to two of his sons, but not the other. Sometimes people who carry a dominant gene do not always show it - if your husband does not have preaxial polydactyly, it could be that he has the gene, but it was not expressed, or the gene came from the other side of the family.

Also, if there are other birth defects along with the polydactyly, this may be part of a genetic syndrome. The inheritance would depend on what the syndrome is.

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Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University