Genetics

Genetic Signals "switches"
When the skeleton is forming in the embryo, a genetic signal instructs the body where and in what size and shape to form bone. In FOP, a gene mutation alters these instructions and leads to malformation of the big toes, a finding often noted at birth. A genetic signal later tells the body after birth to form extra bone at an improper time and place. A mutation of a single gene is likely responsible for all of the skeletal malformations of FOP. The goal of research is to find that gene and stop it from doing harm.

Patterns of Inheritance
FOP is an autosomal dominant condition.This means that a person who carries the gene for FOP will have FOP. In most cases, FOP is a new mutation, or an accident of nature. A sibling or other family member who does not have FOP is no more likely to have a child who has FOP than a person in the general population: that is, one chance in two million. Parents who do not have FOP should be assured that the chance of having a second child with FOP is extremely remote. Though most cases arise from unaffected parents, a person with FOP has a 50% chance of passing it on to a child.

Finding the FOP Gene
On April 23, 2006, researchers at the University of Pennsylvania School of Medicine reported that they had located the “skeleton key,” a gene that, when damaged, causes the body's skeletal muscles and soft connective tissue to undergo a metamorphosis into bone, progressively locking joints in place and rendering movement impossible. Identifying the gene that causes fibrodysplasia ossificans progressiva (FOP), one of the rarest and most disabling genetic conditions known to humans and a condition that imprisons its childhood victims in a “second skeleton,” has been the focus at Penn's Center for Research in FOP and Related Disorders for the past 15 years. This important discovery is relevant, not only for patients with FOP, but also for those with more common skeletal conditions. To learn more about this discovery, please click here.

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