Guidebook Home

Table of Contents

Preface

Introductory Comments

General Questions About FOP

Genetics of FOP

How FOP Affects the Body

Care and Treatment

Activities

Feelings About FOP

Helpful Addresses

Family Resources

Ideas for Independence

Medical Articles

Acknowledgments and Contributions

How does a person get FOP?
The instructions to make a new human being result from genetic information (DNA) from both the mother and father. After birth, genetic information continues to provide the instructions that are necessary for growth and development during childhood and into adulthood. In the case of a child who has FOP, the cells read the genetic information and encounter an instruction -- one that is a change, or mutation, in the normal genetic instructions-- which tells the body to make bone where it should not. This marks the beginning of FOP. If scientists knew exactly which genetic message signals the body to generate extra bone, they might be able to stop the growth from happening. Scientists estimate that there are 50,000 to 100,000 pieces of genetic information, or genes, in each of our cells. At this time, researchers do not know which gene or genes (functional regions of the DNA in chromosomes) are involved in FOP.They also do not know what causes the "genetic switch" which controls FOP to turn on and off at various stages in an individual's life.

What is the relationship between the congenital toe malformation and the extra bone that appears later in childhood?
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. 

Can FOP be prevented?
At the present time, no known prevention exists for FOP. The unknown genetic mutation that leads to FOP occurs spontaneously either in the egg or sperm cell prior to fertilization or just after fertilization in the very early embryo. At present, there is no way to detect these early changes and no known direct cause for their occurrence. Most changes in DNA occur spontaneously without any known cause and have no obvious effect. Some can be beneficial while others can lead to the development of disorders like FOP.

If one child has FOP, what is the chance that a second child will have it?
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. Siblings should be reassured that having a brother or sister who has FOP does not mean that their children will have FOP.

However, researchers have seen one family where perfectly normal parents conceived two affected children. In that family, at least one parent likely had several affected egg cells or sperm cells, despite his or her normal genetic make up. In this family, the chance of a second child having FOP is about 3% (3 chances in 100).

An individual who has FOP has a 50% chance of passing it on to a child. At present, a genetic test for FOP does not exist. If you have concerns about inheritance, genetic counseling may be helpful.

Can people with FOP conceive and have children?
While it may be possible for women who have FOP to conceive and have children, it is dangerous and life-threatening. The extra bone in the chest, abdomen, and pelvis severely limits the ability of the mother's body to adapt to the growth of the baby in the womb.This is detrimental not only to the baby, but especially to the mother whose vital organs are already overcrowded by the extra bone. As a result, very few people with FOP have children.This unfortunately has resulted in the mistaken impression that people who have FOP are unable to conceive and have children.

Due to the genetic nature of FOP, there is a 50% chance that the children of an affected individual (male or female) will develop the disease. There are well documented cases in which FOP has been passed from parent to child, a fact that raises other relevant concerns.

Apart from the biological ability to have children, most people who have FOP will have a hard time dealing with the physical needs of a child as a result of their own physical disability. After considering all of the risks, if a person with FOP still desires to have children, genetic and family counseling is recommended strongly.