- Multiple etiologies:
- Secondary to tissue injury, such as surgery, trauma or infection
- Secondary to conditions which cause calcification: certain tumors (e.g., pilomatrixoma, BCC, chondroid syringoma), collagen vascular diseases (especially CREST syndrome), childhood dermatomyositis, old scars and scleroderma
- Primary (osteoma cutis)
- Miliary osteomas of the face: multiple small, hard papules related to acne scars
- Nevus of Nanta: melanocytic nevus with osteoma
- Various inherited disorders: Gardner's syndrome, Albright's hereditar osteodystrophy, alkaptonuria, ochronosis
- Dermal or subcutaneous trabeculae of lamellar bone
- Osteoblasts and/or osteoclasts may be present.
- Hematopoiesis is usually abesent from the marrow spaces, but may occasionally be seen.