- Author: Luke Lennox, MD; Chief Editor: William D James, MD more...
Strictly defined, osteoma cutis refers to the presence of bone within the skin in the absence of a preexisting or associated lesion. This is opposed to secondary types of cutaneous ossification that can occur in 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 (as in endochondral ossification of the skeletal system).
The lesions of osteoma cutis differ from calcinosis cutis in that they represent bone formation (dermal deposition of hydroxyapatite crystals) versus calcium salt deposits.
The pathogenesis of primary osteoma cutis has the following two proposed mechanisms :
- Through mesenchymal cells differentiating into osteoblasts and then migrating to an abnormal location
- Through an osteoblastic metaplasia of mesenchymal cells already in the dermis, such as fibroblasts
Although considered rare, with no well-defined data on incidence, a plethora of conditions and syndromes may be found in association with osteoma cutis. Hence, the frequency of its occurrence varies accordingly. Primary lesions with no underlying cause are even rarer, but they account for approximately 20% of all skin ossifications. Reported in 1977, of 20,000 consecutive skin biopsies, only 35 cutaneous osteomas were found. Ten of them were primary, while 25 appeared secondary to another abnormality (although long ago, this allows some insight into its rarity).[1, 2]
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. Of note, multiple miliary osteoma cutis classically presents in middle-aged white women.
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