Subungual exostosis

LAST UPDATED: Nov 19, 2021

Introduction

A subungual exostosis is an isolated slow‐growing benign osteochondral outgrowth from the distal phalanx, which arises from under the nail.

This chapter is set out as follows:

Aetiology
History
Clinical findings
Images
Investigations
Management

Aetiology

The cause is unknown

History

A subungual exostosis may occur at any age, but half of the cases arise by 20 years of age

Clinical findings

The big toenail is affected in three-quarters of cases. Less commonly it affects other toes, or the fingers, most commonly the index and middle fingers

A firm nodule develops from beneath the nail bed. The nodule usually grows slowly over weeks to months, and develops a thick hyperkeratotic surface. As it enlarges the nodule causes the nail plate to separate from the bed

Clinical Images

Please refer to notes on image rights at bottom of the page with regards to individual image ownership.

Investigations

An X-ray usually confirms the diagnosis, although early lesions, mostly formed from cartilage, may not be visible

Management

Treatment is by surgical resection

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