Strictly defined, osteoma cutis refers to the presence of bone within the skin in the absence of a preexisting or associated lesion, as opposed to secondary types of cutaneous ossification that occur by metaplastic reaction to inflammatory, traumatic, and neoplastic processes.[1, 2]
Bone arises in skin and soft tissues through mesenchymal (membranous) ossification without cartilage precursors or models (enchondral ossification, as in the skeletal system).
The lesions of osteoma cutis differ from tumoral calcinosis in that they represent bone formation, and calcinosis refers to calcium salt deposits.
In addition to colonic polyposis, epidermal cysts of the face and the scalp, and multiple fibromas, osteomatosis in the form of intraosseous (not cutaneous) osteomas may develop within the membranous bones of the head in Gardner syndrome.
Although said to be rare, with no well-defined data on the incidence, a plethora of conditions and syndromes may be found in association with osteoma cutis, and the frequency of its occurrence varies accordingly. Primary lesions with no underlying cause are even rarer, but they account for approximately 20% of all cases.
Osteoma cutis is not life threatening, although local discomfort and/or disfigurement may lead the patient to seek consultation.
No particular race is predisposed to developing osteoma cutis.
Generally, no distinct sexual predominance exists. However, one cause of osteoma cutis, Albright hereditary osteodystrophy, occurs with a female-to-male ratio of 2:1.
Osteoma cutis may occur at any age.
Osteoma cutis is a feature in several groups of patients.
Small spicules to large masses of mature bone are found in the dermis or extend into the subcutaneous tissue. Spicules of bone may enclose areas of mature fat, recapitulating a medullary cavity, but hematopoietic elements are seldom observed.
A microscopic view of osteoma cutis shows well-formed mature trabecular bone just beneath the epidermis. Note the absence of hematopoietic elements in....