Mutations in the single nucleotide of the ACVR1 gene (also referred to as ALK2) are identified in approximately 97% of FOP patients, particularly the c.617G>A mutation, which results in an arginine-to-histidine substitution at codon 206 (p.R206H)16, 19. The gene discussed is ACVR1; the disease is fibrodysplasia ossificans progressiva.