ACVR1 (587T>C) mutation in a variant form of fibrodysplasia ossificans progressiva: second report.

Fibrodysplasia ossificans progressiva (FOP) is a rare, congenital disorder caused by heterozygous mutation of the bone morphogenetic protein type I receptor ACVR1. Various forms of atypical FOP have recently been identified, and a novel mutation, ACVR1 (587T>C), was reported in 2011. We report on the second patient worldwide with ACVR1 (587T>C) mutation. A 22-year-old Japanese male with no family history of heterotopic ossification did not show any malformation of the great toes and showed normal development from birth to the age of 17 years, when heterotopic ossification appeared in the lumbar area. The clinical symptoms were similar to those reported previously: the delayed onset with a slower and mild clinical course and little finger camptodactyly. Gene analysis revealed that the patient was heterozygous for ACVR1 (587T>C) mutation, the same one as reported in 2011, suggesting a correlation between the location of the mutation and the clinical symptoms. This second report of ACVR1 (587T>C) mutation worldwide is particularly meaningful in that it highlights the difference between clinical symptoms of the first reported patient with ACVR1 (587T>C) mutation and those of classic FOP.