|LETTER TO EDITOR
|Year : 2015 | Volume
| Issue : 2 | Page : 43-45
Solitary stony hard plaque over the scalp in a young adult: A case report
Mukunda Ranga Swaroop1, Periasamy Vasudevan1, Kuchangi C Nischal2, Belagola D Sathyanarayana1
1 Department of Dermatology, Adichunchanagiri Institute of Medical Sciences, Mandya, Karnataka, India
2 Consultant Dermatologist, Nirmal Skin and Hair Clinic, Bangalore, Karnataka, India
|Date of Web Publication||6-Jan-2016|
Mukunda Ranga Swaroop
Department of Dermatology, Adichunchanagiri Institute of Medical Sciences, Mandya, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Swaroop MR, Vasudevan P, Nischal KC, Sathyanarayana BD. Solitary stony hard plaque over the scalp in a young adult: A case report. Indian J Dermatopathol Diagn Dermatol 2015;2:43-5
|How to cite this URL:|
Swaroop MR, Vasudevan P, Nischal KC, Sathyanarayana BD. Solitary stony hard plaque over the scalp in a young adult: A case report. Indian J Dermatopathol Diagn Dermatol [serial online] 2015 [cited 2022 Jan 24];2:43-5. Available from: https://www.ijdpdd.com/text.asp?2015/2/2/43/173417
Osteoma cutis (OC) is a rare and benign disease characterized by the formation of bone tissue in dermis and subcutaneous tissue. It presents in children and adults with a female preponderance.  It is classified as primary OC (15%) wherein bone tissue formation occurs in skin without any pre-existing lesions or is associated with syndromes such as Albright's hereditary osteodystrophy (AHO) and secondary OC (85%) wherein osseous tissue formation occurs in preexisting lesions.  To date, very few cases of isolated plate-like OC have been reported worldwide. We are describing a case of adult-onset plate-like OC over the scalp of 4 years' duration.
A 28-year-old man presented with a slowly growing, asymptomatic, raised lesion over the scalp for the past 4 years. There was no history of itching, pain or bleeding at the site of the lesion. He had no history of prior trauma or any previous cutaneous lesions on the scalp. There was no history of similar lesions in the family members. On clinical examination, a solitary, well-defined, stony hard plaque of size 2 cm × 1 cm, was present over the vertex of the scalp [Figure 1]. He did not have any features suggestive of AHO.
|Figure 1: A solitary, well-defined stony hard plaque of size 2 × 1 cm over the vertex|
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Complete blood count (CBC), serum calcium and phosphorus, serum electrolytes, and liver and renal function tests were within normal limits. Punch biopsy from the lesion revealed a focus of ossification in the dermis [Figure 2]. The ossified focus showed hollow areas containing capillaries, ground substance, collagen, and fibroblasts. There was a foreign body granuloma around the ossified focus, composed of foreign body giant cells, epithelioid cells, histiocytes, neutrophils, and lymphocytes [Figure 3]. The adjoining epidermis showed hypergranulosis and basket weave orthohyperkeratosis.
|Figure 2: H and E stain (100×): Focus of ossification in the dermis showing hollow areas containing capillaries, ground substance, collagen, and fibroblasts|
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|Figure 3: H and E stain (100×): Foreign body granuloma around the ossified focus, composed of foreign-body giant cells, epithelioid cells, histiocytes, neutrophils, and lymphocytes|
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Based on history, clinical examination, and histopathological findings, adult-onset plate-like OC was diagnosed.
OC is a rare and benign disease, characterized by the formation of mature lamellar bone within the dermis and subcutaneous tissue. The first case of OC was reported in 1858 by Wilckets.  It is classified into primary and secondary forms.  Primary OC may occur either de novo or in association with syndromes such as AHO, fibrodysplasia ossificans progressiva or progressive osseous heteroplasia (POH). ,
Secondary OC is the most common variant (85%), wherein the ossification process occurs in pre-existing inflammatory or neoplastic skin lesions such as acne vulgaris, pilomatricoma, trauma, venous stasis, syringoma, epidermoid cysts, scleroderma, scars, and basal cell carcinoma.  In our case, there was no clinical and histopathological evidence of a pre-existing skin lesion.
The pathogenesis of primary OC is not known. Burgdorf and Nasemann proposed two theories. The first theory suggested anomalous migration of osteoblasts to the skin, whereas the second theory stated metaplasia of fibroblast to osteoblast in the dermis due to mutation in the gene GNAS1, which encodes for a protein known to regulate adenyl cyclase activity. 
OC presents in adults and children with a greater female preponderance. Clinically, primary OC manifests in four clinical patterns:
- Solitary osteom,a presenting as an asymptomatic nodule, occurring at any site, commonly in adults;
- Widespread OC, presenting as multiple generalized subcutaneous nodules in the neonatal period;
- Multiple miliary osteomas of the face, presenting in women with/without acne; and
- Congenital plate-like osteoma in neonates or infants, which manifests as asymptomatic large plaque on the scalp or the extremities. 
However, our patient presented with an asymptomatic stony hard plaque over the scalp of only 4 years' duration.
Primary OC may also be associated with syndromes such as, AHO, which is characterized clinically by short stature, round facies, brachydactyly, developmental delay, café au lait macules, and fibrous dysplasia of long bones. It is also associated with hypocalcemia, hyperphosphatemia, and elevated serum parathyroid hormone levels, , which in our case was excluded by physical and laboratory evaluation.
Worret and Burgdorf first coined the term "congenital plate-like osteoma cutis" in 1978 with the following diagnostic criteria:
- Lesion present at birth or within the first year of life;
- No evidence of abnormal calcium or phosphorous metabolism;
- No history of infection, trauma, or other predisposing events; and
- Presence of at least one bony plate with or without cutaneous osteomas. 
Since that time, there have been other reports of plate-like OC that do not present in the first few years of life. Till date, less than 15 cases of acquired, idiopathic, plate- or plaque-like primary OC have been reported, , the most common location being the head and scalp in men.  Our patient presented with a solitary asymptomatic plaque on the scalp of 4 years' duration with no secondary findings both clinically and histopathologically. Hence we arrived at the diagnosis of acquired, adult-onset plate-like OC.
Histologically, OC is composed of a well-circumscribed nodule of mature lamellar bone, completely calcified and inhabited by osteocytes, often containing marrow spaces, present within the dermis. 
Surgical excision is the treatment of choice for plate-like OC. Other modalities of treatment are erbium:YAG laser, dermabrasion, and topical application of retinoids. ,
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]