TMPRSS6 and fibrodysplasia ossificans progressiva: This is corroborated by the work of Pagani et al., who demonstrated proof of this concept by means of a patient carrying an activin receptor 1A (ACVR1A)/TMPRSS6 compound heterozygous genotype, presenting with fibrodysplasia ossificans progressiva (FOP) as well as an IRIDA phenotype [45].