Accessory nail of the right index finger following trauma

A 35-year-old man presented with a hard, curved, nail-like projection arising adjacent to the right ring-finger nail for 1 year. The lesion was asymptomatic. He reported a history of trauma to the same finger 2 years earlier. Examination revealed a separate, well-defined, translucent keratin plate distal to the proximal nail fold, distinct from the main nail [Figure 1]. Dermoscopy was performed using contact polarized (10x) mode with a liquid interface, which demonstrated parallel longitudinal striations with a smooth, shiny surface, and absence of vascular or hemorrhagic structures, consistent with an accessory (ectopic) nail [Figure 2]. The patient was counseled regarding the benign nature of the lesion. Surgical excision was advised; however, he opted for conservative management as the lesion was asymptomatic.

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Figure 1:

Clinical image showing a separate, curved, nail-like keratin plate adjacent to the right index fingernail.

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Figure 2:

Parallel longitudinal ridges and a smooth, shiny nail-like surface without vascular structures. (Dermalite, contact polarized, 10x).

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Ectopic nail (onychoheterotopia) is a rare entity, with fewer than 100 cases reported in the literature.^[1] It may be congenital or acquired following traumatic implantation of nail matrix cells. Surgical excision of the ectopic matrix is the definitive treatment.^[2] Recognition of this benign condition prevents misdiagnosis as onychomatricoma or cutaneous horn.