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Dermatology > METABOLIC DISEASES
Osteoma Cutis
Article Last Updated: Oct 19, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 9  
Author: Kevaghn P Fair, DO, Consulting Staff, Department of Pathology, Dominion Pathology Laboratories
Kevaghn P Fair is a member of the following medical societies: American Society of Clinical Pathologists, American Society of Dermatopathology, and College of American Pathologists
Editors: James W Patterson, MD, Director of Dermatopathology, Professor of Pathology and Dermatology, Departments of Pathology and Dermatology, University of Virginia Medical Center; David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Director Dermatology Residency Training Program, Scott and White Clinic; Rosalie Elenitsas, MD, Associate Professor of Dermatology, University of Pennsylvania School of Medicine; Director, Penn Cutaneous Pathology Services, Department of Dermatology, University of Pennsylvania Health System; Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University; William D James, MD, Paul R Gross Professor of Dermatology, University of Pennsylvania School of Medicine; Vice-Chair, Program Director, Department of Dermatology, University of Pennsylvania Health System
Author and Editor Disclosure
Synonyms and related keywords:
bone in the skin, Albright hereditary osteodystrophy, Albright's hereditary osteodystrophy, miliary osteomas
Background
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.
Pathophysiology
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.
Frequency
United States
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.
Mortality/Morbidity
Osteoma cutis is not life threatening, although local discomfort and/or disfigurement may lead the patient to seek consultation.
Race
No particular race is predisposed to developing osteoma cutis.
Sex
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.
Age
Osteoma cutis may occur at any age.
History
- Patients may report having hard areas in the skin.
- A familial occurrence of Albright hereditary osteodystrophy may be present.
Physical
- The presentations of osteoma cutis can be highly variable, with clinical entities that are defined by the number, the form, and the location of the lesions.
- Osteomas may present as single or multiple, extremely hard nodules, plaques, or miliary tumors.
- The face, the extremities, the scalp, the digits, and the subungual regions are the most commonly affected sites.
Causes
Osteoma cutis is a feature in several groups of patients.
- Albright hereditary osteodystrophy, which includes most patients with pseudohypoparathyroidism and pseudopseudohypoparathyroidism, is due to an autosomal dominant defect in the alpha subunit of intracellular guanyl nucleotide-binding protein (G protein).
- The characteristic phenotype includes short stature, a round face, defective teeth, mental retardation, brachydactyly, and osteomas of the soft tissue and the skin.
- Tetany is often the presenting sign of pseudohypoparathyroidism, formerly called Albright hereditary osteodystrophy. In addition to skeletal system abnormalities, lesions of osteoma cutis are frequently observed.
- Single, small osteomas, arising later in life, sometimes with transepidermal elimination of bony fragments may be a cause.
- Multiple, miliary osteomas of the face, following acne, neurotic excoriation, or dermabrasion is a possible cause.
- Congenital plaquelike osteomatosis or limited dermal ossification is generally present from birth; the skin of the scalp or the extremities is often affected.
- Fibrodysplasia ossificans heteroplasia and fibrodysplasia ossificans progressiva are possible causes.
- Miscellaneous rare disorders with or without cartilaginous elements include osteomas of the distal extremities and multiple osteomas of childhood unrelated to Albright hereditary osteodystrophy.
Calcinosis Cutis
Other Problems to be Considered
Cartilaginous tumors of the skin
Foreign body
Gouty tophus
Myositis ossificans
Secondary (heterotopic) ossification
Lab Studies
- Serum calcium and parathyroid hormone (PTH) levels help to define Albright hereditary osteodystrophy.
Imaging Studies
- Plain radiographs demonstrate lesions but are not necessary for diagnosis.
Procedures
- Excisional biopsy for diagnosis, relief of discomfort, or cosmesis may be performed.
Histologic Findings
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 (see Image 3).
Medical Care
- Removal by excision or laser resurfacing to unroof overlying skin may be performed. Treatment with the Er:YAG laser may result in less hypopigmentation and scarring than with the carbon dioxide laser.
- Other reported treatments with unproven efficacy include the following:
- Topical application of tretinoin to provoke transepidermal elimination
- Etidronate disodium taken orally
Consultations
When several lesions are noted, especially in pediatric patients, evaluation for associated syndromes may be warranted.
Prognosis
- Osteosarcoma or other malignancies have not been reported to arise within osteoma cutis.
| Media file 1:
Solitary nodule on the frontal part of the scalp. |
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| Media file 2:
Miliary cutaneous osteomata. Multiple, small, bluish, stony-hard nodules in an acneiform distribution along the cheeks. |
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| Media file 3:
A microscopic view of osteoma cutis shows well-formed mature trabecular bone just beneath the epidermis. Note the absence of hematopoietic elements in the medullary spaces. |
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Media type: Photo
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- Weedon D, ed. Skin Pathology. 2nd ed. New York, NY: Churchill Livingstone; 2002:. 355-7.
Osteoma Cutis excerpt Article Last Updated: Oct 19, 2006
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