Progressive osseous heteroplasia

Background: Primary heterotopic ossification beginning in childhood is quite rare but occurs in several well-described conditions, such as Albright hereditary osteodystrophy, fibrodysplasia ossificans progressiva, and platelike osteoma cutis. Recently, a new disorder called progressive osseous heteroplasia (POH) has been described in the orthopedic literature. Primary cutaneous calcification and ossification beginning in infancy are presenting signs of this progressive and potentially debilitating disorder. Observations: We describe 2 children with POH who were recently seen at Children's Hospital of Wisconsin. Both children were female and developed cutaneous calcification and ossification within the first 6 months of life. Both girls had progression of the lesions to involve ossification of the deeper tissues. No abnormalities in calcium, phosphorus, vitamin D, or parathyroid hormone levels were identified in these patients. No associated anomalies were detected. Biopsy results from the lesions showed calcinosis cutis superficially, with both endochondral and intramembranous bone formation in the deeper tissues. Conclusions: Progressive osseous heteroplasia must now be included in the differential diagnosis of primary cutaneous ossification beginning in childhood. Because the first clinical manifestations of POH appear in the skin, it is important for dermatologists to be aware of this newly described condition.