A rare disease characterized mainly by connective tissues becoming ossified or turning into bone, due to a defective gene (e.g. ACVR 1)
Fibrodysplasia ossificans progressiva (FOP) is an extremely rare disease affecting the connective tissues. The condition is characterized by the fibrous tissue becoming ossified or turning into a bone. Thus, it is also called stoneman disease. As of 2017, there were only about 800 cases that had been reported since.1
This condition is caused by a genetic mutation affecting the repair mechanism of the body. Thus, tissue injury in an individual suffering from FOP fails to heal normally, and rather, ossifies or tends to be repaired with extra bone growths at the site of injury. Thus, injuries at the joints would hamper mobility. Furthermore, fibrous tissues may also be spontaneously ossified.
One of the possible causes of FOP is a genetic mutation in the ACVR1 gene. This gene encodes activin receptor type-1 protein. A mutation resulting in the substitution of codon 206 from arginine to histidine in the said protein leads to its activation and subsequently to the transformation of connective tissue (as well as muscle tissue) into a secondary skeleton.2
1 Martelli, A. and Santos, A. R. Jr (2014). “Cellular and morphological aspects of fibrodysplasia ossificans progressiva. Lessons of formation, repair, and bone bioengineering”. Organogenesis (Review). 10 (3): 303–11.
2 Fibrodysplasia ossificans progressive: causes. Wikipedia.org (web). Retrieved from https://en.wikipedia.org/wiki/Fibrodysplasia-ossificans-progressiva#Causes.