Onychomatricoma is rare benign tumor of the nail matrix that was first described in 1992. It is seen in both men and women and is more common in individuals of Northern European descent. It is seen on both fingernails and toenails but is slightly more common on the fingernails.

It is believed that onychomatricomas form due to abnormal nail matrix differentiation. Trauma and onychomycosis may play a role. Array-based comparative genomic hybridization showed genomic losses on chromosome 11.

Onychomatricoma is rare in children with only one case described to date.