Osteoma cutis D23.0

Rare, benign, congenital or later manifesting, mostly multiple skin tumors, which are caused by dermal ossification.

A distinction is made between:

• primary (neoplastic)
• secondary (metaplastic) osteomas.

The classification of osteomas is not uniform. Some authors use the term "osteoma cutis" only for primary ossifications that do not occur in the context of osteodystrophia hereditaria. S.a. Osteosis cutis multiplex.

In primary osteomas the cause is unclear. Discussed are a transformation of omnipotent connective tissue cells into osteoblasts, a dislocation of bone germ centres, the perception of the osteoma as a hamartoma and an inherited predisposition.

In secondary osteomas (heterotopic ossification), chronic inflammatory processes, especially in acne vulgaris, trauma, chronic venous insufficiency, endocrinological disorders (pseudohyperparathyroidism) form the basis for heterotopic ossification. Here, metaplasia is discussed, whereby mesenchymal cells in a suitable inflammatory milieu) differentiate into osteoblasts.

Mainly occurring on the capillitium (osteomas of the scalp) or face (osteosis multiplex faciei).

Pinhead size, rough nodules and/or extensive hard, bumpy infiltrates. Childhood osteomas are also a concomitant symptom of pseudohypoparathyroidism.

All forms of cutaneous ossification require the detection of mature, lamellar bone tissue at the cutis-subcutaneous border. There are irregularly shaped bone bundles, in the marginal areas osteoblasts and osteoclasts in Howship's lacunae. Osteoid is detectable. Secondary ossification can be distinguished from primary ossification by the fact that a connection to a pre-existent process can still be established (e.g. to an inflammatory or neoplastic process).

Cosmetically or functionally disturbing foci can be addressed surgically. Small osteomas are treated by incision or pricking, larger foci are excised. Trials with dermabrasio and tretinoin are partly successful. Subsequent increased occurrence of osteomas is described in some cases!

Therapeutic approaches with diphosphonates such as etidronic acid (e.g. Diphos) have been tried in some patients without significant effect.

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