Three Pairs of Monozygotic Twins With Fibrodysplasia Ossificans Progressiva The Role of Environment in the Progression of Heterotopic Ossification

Genetic and environmental factors affect the phenotype of fibrodysplasia ossificans progressiva (FOP) but their relative effects are unknown. We studied three pairs of monozygotic twins with FOP and found that, within each pair, congenital toe malformations were identical. However, postnatal heterotopic ossification varied greatly depending on life history and environmental exposure. This study shows that genetic determinants strongly influence disease phenotype during prenatal development and that environmental factors strongly influence postnatal progression of the disease.