Giant onychomatricoma*

©2018 by Anais Brasileiros de Dermatologia Dear Editor, Onychomatricoma (OM) is a rare benign neoplasm of nail matrix origin. The disease was first described by Baran and Kint in 1992 in a report of three cases.1 In some cases, it may present itself with important nail dystrophy, which makes its diagnosis a challenge. We report a rare case of OM in which we discussed the clinical and dermoscopic aspects of an exuberant lesion. An 80-year-old male patient presented with an asymptomatic onychodystrophy on the left third toe beginning five years before. His pathological history revealed systemic arterial hypertension and dyslipidemia, without regular use of medications. On clinical examination we observed periungual erythema and a palpable hardened nodule on the proximal nail border, as well as xanthonychia and important onychodystrophy extending vertically from the nail bed in a filiform pattern (Figure 1). Onychoscopy of the nail plate revealed proximal splinter hemorrhages, white transverse lines, and yellowish areas (Figure 2). At the free edge of the nail, we observed dark cavitations in the middle of the subungual keratosis. After avulsion of the matrix and excision of the tumor, histopathological examination revealed epithelial proliferation in the nail matrix, sometimes papillomatous, and fibrous stroma, confirming the diagnosis of onychomatricoma (Figure 3). Onychomatricoma is a rare, slow-growing neoplasm of the nail matrix – asymptomatic in most cases – that may rarely present with pain.2,3 It mainly affects Caucasian women around the age of 50. It is more common on the fingers than on the toes. However, this conclusion is questionable, since it is an asymptomatic lesion, and consequently, its alterations tend to be more noticeable when they occur on the fingers.2,3,4 Classically, it manifests itself with the formation of a nail plate of variable thickness, accentuation of the transverse curvature, splinter hemorrhages in the proximal portion, FIgure 1: Clinical examination. Third toe with important onychodystrophy and an erythematous nodule on the proximal nail border