In conclusion, we described 16 Polish patients diagnosed with FOP, 13 carrying the p.Arg206His pathogenic variant, two having the p.Gly356 Asp pathogenic variant, and one harboring the p.Arg258Ser pathogenic variant in ACVR1. Our results broaden the phenotypic and genotypic landscape of FOP, providing relevant information about genotype–phenotype correlations of the condition. The gene discussed is ACVR1; the disease is fibrodysplasia ossificans progressiva.