Onychoheterotopia: pathogenesis, presentation, and management of ectopic nail

Onychoheterotopia is an extremely rare condition in which the nail tissue grows outside the classic nail unit of the dorsal fingers and toes. It presents as either small outgrowths of a deviant nail or a complete double fingernail malformation. The histology of the onychoheterotopia matrix is oftentimes very similar to the normal nail matrix, although it plays a central role in diagnosis.

We sought to review the current literature on the clinical and histologic aspects of onychoheterotopia.

A literature search was performed to evaluate peer-reviewed articles on the topic.

Detailed reports have characterized many features of onychoheterotopia. The various etiology and treatment options are reviewed.

The study was limited to those articles in the English-language literature.

In this article, we provide a review of the literature based on the current understanding of onychoheterotopia, its diagnosis, and its management.