<h2>Introduction</h2> Fibrodysplasia ossificans progressiva is an extremely rare and disabling genetic condition characterized by progressive heterotopic ossification of soft tissues such as muscles, ligaments, tendons, fasciae, and aponeuroses. The prevalence of fibrodysplasia ossificans progressiva is estimated to be about one in 2 million individuals 1 . Heterotopic ossification in fibrodysplasia ossificans progressiva usually begins in the first decade of life with the episodic development of inflammatory fibroproliferative masses in the axial skeleton. Most patients with fibrodysplasia ossificans progressiva are misdiagnosed as having soft-tissue sarcoma or aggressive juvenile fibromatosis before the definitive appearance of heterotopic ossification and undergo invasive procedures that usually lead to the acceleration of ossification 2 . Early correct diagnosis of fibrodysplasia ossificans progressiva is necessary to prevent additional iatrogenic harm or trauma. At the molecular level, dysregulated bone morphogenetic protein (BMP) signaling is associated with the formation of heterotopic ossification in fibrodysplasia ossificans progressiva. Patients with classical features of the disease have the same heterozygous missense mutation in the glycine-serine activation domain of activin A receptor type-I gene (ACVR1), a BMP type-I receptor 3 . The causative mutation of fibrodysplasia ossificans progressiva is a recurrent single-nucleotide substitution at position 617 (c.617G>A; R206H) in the ACVR1
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