Late-Onset Progressive Osseous Heteroplasia: 2 Unrelated Cases and Use of Positron Emission Tomography for Diagnosis.

Progressive osseous heteroplasia (POH) is a rare autosomal-dominant hereditary bone disorder caused by inactivating pathogenic variants in GNAS1. POH is characterized by progressive cutaneous ossification and heterotopic ossification in skeletal muscles and subdermal connective tissues. Understanding of the natural history and phenotypic heterogeneity of the illness is incomplete. We report 2 affected male subjects with a milder than usual clinical course, highlight their clinical presentations and molecular correlates, and propose sodium ¹⁸F-fluorine positron emission tomography (PET) scanning as a sensitive technique for POH diagnosis and management.