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Acquired plate-like osteoma cutis

  • Author(s): Vashi, Neelam
  • Chu, Julie
  • Patel, Rishi
  • et al.
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Acquired plate-like osteoma cutis
Neelam Vashi MD, Julie Chu MD, Rishi Patel MD
Dermatology Online Journal 17 (10): 1

Department of Dermatology, New York University, New York, New York

Abstract

Plate-like osteoma cutis is a rare disorder that has been historically classified as a congenital syndrome. It has a possible relationship to a mutation in the gene (GNAS1) that encodes the α-subunit of the stimulatory G protein, which regulates adenyl cyclase activity. We report a case of extensive plaque-like masses on the scalp and face with no abnormalities in calcium or phosphate metabolism and no preceding inflammatory cutaneous conditions. With less than ten reported cases, to our knowledge, this is one the few cases of acquired plate-like osteoma cutis described in the literature.



History


Figure 1Figure 2

Figure 3Figure 4

A 50-year-old man presented to the dermatology clinic at the Charles C. Harris Skin and Cancer Pavilion in June, 2010, for evaluation of multiple, thick, crusted plaques on his scalp and face. The lesions first appeared as small growths approximately 31 years ago. Over the past several years, they had been increasing in size and had spread to his chest and legs. He reported pain and recurrent infections that were associated with the lesions. Topically, salicylic acid and tretinoin gel were used without relief. He had surgery four times for attempted removal of the plaques; however, these procedures had failed to provide benefit. He had no family history of skin diseases. He had no history of prior trauma, antecedent infections, tetracycline use, acne, or other inflammatory skin disorders. He took no medications and had no known allergies to medications.


Physical examination

Multiple, indurated, coalescing plaques with overlying crusted erosions and superficial ulcers were present on the scalp. Multiple, indurated, erythematous plaques were noted on the cheeks. Multiple, indurated hyperpigmented papules were present on the left side of the chest and on the anterior aspects of the thighs.


Laboratory data

Calcium, phosphorus, and parathyroid hormone levels were normal.


Histopathology


Figure 5

There is a well-circumscribed, nodular aggregate of partially mineralized bone adjacent to a hair follicle.


Discussion

The formation of bone through the deposition of calcium and phosphorus in a proteinaceous matrix as hydroxyapatite crystals is known as ossification [1]. Osteoma cutis is a rare skin disorder of cutaneous ossification, in which mesenchymal stem cells differentiate into bone outside the context of the normal skeleton. Although a benign skin condition, the disease may have appreciable psychological consequences because the associated cutaneous deformities.

Osteoma cutis can be classified as primary or secondary. When primary, there are four associated syndromes: fibrodysplasia ossificans progressiva, Albright hereditary osteodystrophy (AHO), progressive osseous heteroplasia (POH), and plate-like osteoma cutis. These four syndromes present with specific phenotypes, metabolic dysfunctions, and associated findings. Fibrodysplasia ossificans progressiva is unique in that the mechanism of bone formation is endochrondral. The other three entities show more clinical overlap as they all involve intramembranous ossification that begins in the dermis [1].

Genetic analyses have provided evidence of a pathogenic relationship between these three disorders in that they all have mutations in the gene (GNAS1) that encodes the α-subunit of the stimulatory G protein that regulates adenyl cyclase activity [2, 3, 4, 5]. These inactivating mutations likely produce reduced levels of downstream proteins that are insufficient to maintain inhibitory control of cellular induction to osteoblast differentiation in ectopic sites [3].

General distinguishing characteristics have been noted among the three entities. AHO has associated findings that may include pseudohypoparathyroidism or pseudo-pseudohypoparathyroidism with obesity, short stature, brachydactyly, and round facies. Cutaneous lesions in POH are generally asymptomatic papules and nodules that appear shortly after birth and that may be rapidly progressive [6, 7]. POH and plate-like osteoma cutis may represent varieties of the same disorder, with the latter being a limited form of POH; the skin lesions appear quite similar [1].

In 1978, plaque-like osteoma cutis was described in a four-month-old infant who had an enlarging bony plate on the lateral aspect of the thigh and knee. Twelve other patients had similar findings [8]. Based on this case series, the term, plate-like osteoma cutis, was coined and the following diagnostic criteria were proposed: lesions present at birth or within the first year of life, no abnormal calcium or phosphorus metabolism, no predisposing event (i.e., infection, trauma), and the presence of at least one bony plate with or without other cutaneous osteomas [8, 9].

Since that time, there have been other reports of plate-like osteoma cutis that do not present in the first few years of life. A review of the literature disclosed seven patients who were reported to have non-congenital forms of plaque-like osteoma cutis [10]. The disease was more frequent in men and on the head [10]. Our patient presented with extensive plaque-like masses on his scalp and face. No abnormalities in calcium or phosphate metabolism were detected and no inflammatory conditions preceded the disease. Owing to the paucity of associated findings, a diagnosis of acquired plate-like osteoma cutis was made.

Treatment for cutaneous ossification is quite difficult. Underlying abnormalities in calcium and/or phosphorus should be addressed. However, when complete ossification has already developed, options are limited. Therapeutic intervention may be medical, surgical, or a combination of both. Surgical techniques are most frequently used [11]. Excision of neoformed bone can be performed via an incision over the lesions and curettage of the bony material with the surgical blade or a small curette, followed by primary suture closure [12]. A needle microincision-extirpation method with incision, curettage, and healing by secondary intention also has been described [13]. Unfortunately, excision often is not practical when the disease is extensive and even with partial or total resection, recurrence may occur.

Dermabrasion and laser resurfacing with curettage of exposed osseous fragments have been employed and reported to be successful with no recurrence. [14, 15, 16]. The erbium:YAG laser has been used to ablate the epidermis and upper dermis, after which the osteoma is removed by simple pressure, light gauze rubbing, or curettage with a fine curette [14, 15, 17]. Topical application of tretinoin to stimulate re-epithelialization and provoke spontaneous transepidermal elimination of the more superficial osseous fragments also has been reported to have beneficial effects [18, 19, 20, 21]. The oral administration of etidronate disodium, which is a drug that inhibits calcium reabsorption, has been shown to be ineffective. Combination therapy with topical retinoids and surgical resection may be a viable approach [22].

Plate-like osteoma cutis represents a rare disorder with limited options for treatment. More research is needed to further decipher etiologic causes, which may include possible congenital or acquired gene mutations, to enable more efficacious therapeutic options.

References

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