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Fibrodysplasia ossificans progressiva (FOP), is a rare disease of the connective tissue. A mutation of the body's repair mechanism causes fibrous tissue (including muscle, tendon, and ligament) to be ossified (turned to bone) when damaged. In many cases they can cause joints to become permanently frozen in place. The growths cannot be removed with surgery because such removal causes the body to "repair" the area of surgery with more bone.
Prognosis
Over time, as more bone grows and the patient loses mobility in more and more joints, it may become impossible for the patient to reach, walk, eat, or even breathe. The disease is usually fatal as bone crushes the internal organs. People with FOP usually lose all mobility by the age of 30 and die by the age of 40. There is no known cure.
Symptoms
Children born with FOP characteristically have short big toes. The first "flare-up" that leads to the formation of FOP bones is usually before the age of 10. Often, the tumor-like lumps that characterize the disease appear suddenly overnight. Because the disease is so rare, the symptoms are often misdiagnosed as cancer. This leads doctors to order biopsies, which can actually exacerbate the growth of these lumps.
Cases
Since the 1800's there have been periodic references in medical literature describing people who literally "turned to stone", and it is possible that some of these cases may have been attributable to FOP.
Perhaps the most well-known FOP case in modern times was that of Harry Raymond Eastlack Jr., who was born in Philadelphia, PA in November, 1933. Mr. Eastlack’s condition began to develop around the age of ten, and at the time of his death from pneumonia in November 1973 (six days before his fortieth birthday), his body had completely ossified, leaving him able to move only his lips.
What makes Mr. Eastlack’s case particularly notable is that shortly before his death, he made it known that he wanted to donate his body to science, in the hope that in death he would be able to help find a cure for this little-understood and particularly cruel disease. As per his wishes, his preserved skeleton now resides in The Mütter Museum (see a Quicktime animation) in the College of Physicians of Philadelphia, and has proven to be an invaluable source of information in the study of FOP.
Treatment
People with FOP should use sound judgement in engaging in physical activity, try to avoid falling or getting bruises, and avoid intramuscular injections since these can cause bone to grow. Likewise, people with FOP should never stretch their joints outside of their normal range of motion. However since flare-ups can occur spontaneously, even perfect preventive care cannot guarantee the absence of bone growths.
Causes
FOP is caused by an autosomal dominant allele on chromosome 2. The allele has variable expressivity, but complete penetrance. Most cases are caused by spontaneous mutation in the gametes; most people with FOP cannot have children. 2000 cases have been reported to date, but a study has determined that it affects approximately 1 in 1.64 million people. A similar but less catastrophic disease is Fibrous dysplasia, which is caused by a post-zygotic mutation.
Researchers from the University of Pennsylvania announced in April 2006 that a mutation in the gene ACVR1 is responsible for the disease. ACVR1 encodes activin receptor type-1, a BMP type I receptor.
Sources
- The International FOP Association
- "Fibrodysplasia ossificans progressiva" WebMDHealth
- http://jmg.bmjjournals.com/cgi/content/abstract/19/1/35
- http://www.blackwell-synergy.com/links/doi/10.1034/j.1399-0020.1999.285280512.x/abs
- http://www.timesonline.co.uk/article/0,,11069-2148620,00.html
References
Congenital disorders | Rare diseases
Fibrodysplasia ossificans progressiva | Progresa osti%C4%9Da fibrodisplazio | Postępujące kostniejące zapalenie mięśni
"Fibrodysplasia ossificans progressiva"