Individuals with fibrodysplasia ossificans progressiva are born with malformations of the
great toes and develop a heterotopic skeleton during childhood because of an identical
heterozygous mutation in the glycine-serine activation domain of ACVR1, a bone
morphogenetic protein type I receptor. Substitution of adenine for guanine at nucleotide 617
replaces an evolutionarily conserved arginine with histidine at residue 206 of ACVR1 in all
classically affected individuals, making this one of the most highly conserved disease …