Classical and Atypical Fibrodysplasia Ossificans Progressiva in India

Summary Fibrodysplasia Ossificans Progressiva (FOP) is a rare debilitating disorder characterized by congenital deformity of the great toes from infancy and postnatal heterotopic ossification. Activating mutations in the activin A receptor type 1 ( ACVR1 ) gene are responsible for the disease. The most common allelic variant leading to FOP is c.617 G>A; p.R206H, however, other alleles have been reported with atypical phenotypes. We report 14 cases presenting to a referral institution in South India over a 3‐year period. The patients were clinically diagnosed based on foot abnormality or abnormal ectopic ossification and were screened for ACVR1 . The genetic analysis of ACVR1 identified the recurrent allelic variant in 12 of 14 patients. One of the remaining patients had a previously reported allele c.1067G>A; p.G356D in the 9th exon and the second allele c.983G>A; p.G328E in the 8th exon of ACVR1 . The most common recurrent allele c.617 G>A; p.R206H is also the most common in Indian patients with FOP.