Fibrodysplasia Ossificans Progressiva in Three Filipino Children

Abstract

Fibrodysplasia ossificans progressiva (FOP) is a debilitating, rare, autosomal dominant disorder of connective tissue characterized by malformed great toes and by progressive endochondral ossification of extra-skeletal sites (e.g., muscles, tendons, fascia) triggered by trauma, soft tissue injury, muscle fatigue, or viral infections. We present three children affected with FOP with this classic clinical presentation, the first reported cases in the Philippines, thus extending the range of classic FOP to new geographic and ethnic locations. Two of the affected children are siblings who have the common ACVR1 R206H mutation associated with classic FOP; this mutation was not found in their parents who are phenotypically unaffected, providing evidence of germline mosaicism in FOP. To our knowledge, this is the first family with genetic testing done showing presence of the classic mutation in affected siblings not seen in the unaffected parents.