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Onychomatricoma in a Patient with Extensive Vitiligo: Answer.

DISCUSSION Onychomatricoma (OM) is a rare, benign, subungual tumor of fibroepithelial cells in the nail matrix. First described in 1992 by Baran and Kint, it is the only tumor in which nail plate changes result from digitiform projections arising from the matrix.1,2 Fewer than 80 cases are reported in the literature. Women are more commonly affected than men, with a peak incidence in the fifth decade. It is often slow growing and painless.2 A clinical tetrad of OM has been described by Perrin et al, which includes xanthonychia, ungual hyperkeratosis, splinter hemorrhages, and longitudinal or transverse overcurvature of the nail plate.3–6 Differential diagnoses may include fibrokeratoma of the nail matrix, onychomycosis, squamous cell carcinoma, Bowen disease, verruca vulgaris, nail fibroma, glomus tumor, and digital mucous cyst.2 Treatment is through surgical excision, and prognosis is often good.5 Depending on the extent of the tumor, regrowth of nail plate may occur with or without dystrophy after complete excision of the tumor.2 Characteristic findings of clinical examination, dermoscopy, histopathology with or without immunohistochemical staining, and/or radiographic imaging may be helpful in establishing the diagnosis of this rare entity. Common clinical features with frequencies in a series of 30 cases described by Di Chiacchio et al are as follows: increased nail thickness (83%), splinter hemorrhages (80%), longitudinal xanthonychia (73%), increased transverse curvature of the nail (50%), erythema and swelling at the proximal nail fold (50%), woodworm-like cavities of the free edge of the nail plate (43%), pain during nail compression (30%), and longitudinal melanonychia (23%).4 Dermoscopy findings may include perforations in the distal nail plate, splinter hemorrhages, and longitudinal parallel white ridges.2,4–6 Ultrasonography may reveal hypoechogenicity near the tumor and hyperechogenicity near the finger-like projections.2 Magnetic resonance imaging may show low uptake near the mail matrix and high uptake near the distal, finger-like projections.2 Onychomatricoma has 2 anatomic zones with distinct histology. The proximal zone, which corresponds to the area beneath the proximal nail fold extending from the root of the nail to the cuticle clinically, shows deep epithelial invagination filled with keratin, a thickened nail plate with ungual spurs near the inferior border, and a fibrillar stroma. The distal zone, which corresponds to the lunula clinically, contains multiple finger-like digitations surrounded by matrix epithelium, perforation of the distal nail plate with multiple cavities filled with serous fluid, and areas of connective tissue that deeply penetrate the stroma.1,6 Ungual nail clipping may reveal thickening of the nail plate with cavities filled with serous material and a thin layer of epithelium on the periphery.2 Immunohistochemical examination may reveal diffuse positive expression of CD10 (onychodermis marker) and CD34 (fibroblast-like mesenchymal cell marker) in the stroma of the OM, negative periodic acid–Schiff staining for fungal element, and cytokeratin positivity of cystic content.2,5 Nail abnormalities in the setting of vitiligo were described by Topal et al7 and were noted to be more prevalent in patients with vitiligo than in the control group. Common nail abnormality findings in the setting of vitiligo include longitudinal ridging, leukonychia, absent lunula, onycholysis, nail bed pallor, onychomycosis, splinter hemorrhage, and nail plate thinning.7 Although the association of cutaneous malignancy with vitiligo is still unclear, vitiligo seems to have a protective effect against melanoma.8 Few cases of OM have been reported in the literature, especially in the setting of other dermatologic comorbidities. We present a case of OM in a 72-year-old woman with extensive vitiligo. Although other nail findings can be seen in patients with vitiligo, to the best of our knowledge, this is the first reported case of OM in the setting of vitiligo.