Subungual Exostosis

Subungual Exostosis

Subungual exostosis is a bony tumor condition that occurs in the distal phalyx, the toe bone furthest from the foot, most frequently on the big toe. The condition presents itself as a protrusion beneath the nail plate, lifting the nail up and away from the skin. It may cause pain when walking, but not necessarily. This condition is common in both sexes for people in their twenties and thirties. The condition can be mistaken for other conditions such as warts, fibroma, paronychia, myositis ossificans, and pyogenic granuloma but can be confirmed by radiography.


Chronic irritation, trauma, and chronic infections beneath the nail bed are considered causative factors. Eventually, the irritated cells grown into and fuse with the phalyx bone.


Initially, this condition may appear as a white mass, create swelling and or a change in pigmentation. As it matures, onycholysis (nail detachment) may occur and paronychia (skin infection) is observed in some patients. Radiography is often prescribed to properly diagnose this condition. Once any malignant tumors have been ruled out, a course of treatment can be determined. Most often, this condition is benign.


Surgery is typically prescribed to remove the bony protrusion and is successful in most cases.