Onychomatricoma: A Rare and Potentially Underreported Tumor of the Nail Matrix

Onychomatricoma is a rare benign neoplasm of the nail matrix first described by Baran and Kint in 1992. Fewer than 80 cases of onychomatricoma have been described in the literature, 15 of which were initially misdiagnosed and treated as onychomycosis. We present the case of a 66-year-old male with thickening and linear xanthonychia of the hallux nail plate secondary to an onychomatricoma misdiagnosed as onychomycosis. Following biopsy for histopathologic analysis, the lesion and proximal nail matrix were surgically excised. At 12 months post-excision, the patient remains asymptomatic without evidence of recurrence. The purpose of the present case report is to make foot and ankle surgeons more cognizant of the pathology, highlight the nonspecific clinical and radiologic findings, and emphasize the importance of interdisciplinary communication for an accurate clinicopathologic correlation and diagnosis of the lesion. Although rare, onychomatricoma should be considered in the differential diagnosis for patients presenting with onychomycosis failing to respond to antimycologic treatment. The clinical index of suspicion for onychomatricoma should increase when only a singular dystrophic nail is involved. Following diagnostic confirmation by histopathology, complete surgical excision is the treatment of choice.