Fibrodysplasia ossificans progressiva is a rare autosomal dominantly inherited disorder of connective tissue caused by mutations in the gene encoding for ACVR1/ALK2, a bone morphogenetic protein type I receptor. It is mainly characterized by congenital malformations of the great toes and the formation of qualitatively normal bone in extra-skeletal sites leading to severe disability and eventual...

BACKGROUND In order to facilitate normal gait, toes require to be in a rectus position during the propulsive phase. This requires a correct balance and sequence of activity of the intrinsic musculature of the feet. Alteration of this balance and sequence may lead to the development of claw toes. Atrophy of the lumbricals occurs in the development of claw toes, but it is not known if changes occ...