Abstract
Progressive osseous heteroplasia (POH) is an ultrarare hereditary disease that begins with cutaneous ossification, and progressive heterotopic ossification involves subcutaneous and deep connective tissues. We reported a case of POH in a five-month-old boy with clinical, pathological, and genetic features of POH. Most POH cases are caused by GNAS inactivating mutations, and the mutation of GNAS is also found in some other related heterotopic ossification conditions. A discussion of the clinical and laboratory features of these disorders is made in our case report.