Onychomatricoma: a rare case of unguioblastic fibroma of the fingernail associated with trauma.

Onychomatricoma (OM) is a rare tumor originating from the nail matrix. Fingernail involvement is twice as common as toenail involvement. Onychomatricoma is the only tumor that actively produces a nail plate. Clinically, it presents with yellow discoloration along the entire nail plate, proximal splinter hemorrhages, and a tendency toward transverse overcurvature of the nail plate with prominent longitudinal ridging. We report a rare case of OM in which the etiology was associated with trauma. Onychomycosis can be present, which may serve as a predisposing factor or be secondary to the deformed nail plate. Histologically, the tumor is fibroepithelial or biphasic with stromal and epithelial components. Onychomatricoma has been further classified into 3 types, including unguioblastoma, unguioblastic fibroma, and atypical unguioblastic fibroma. Our case represents the unguioblastic fibroma type.