Saturday, July 2, 2016

Fingernail Bump

As a hand surgeon, I am often asked questions about fingernails- whether related to irregularity (bumps, pain, swelling) of the nails or pain.  Most of these are minor or temporary issues and there are several excellent reviews on the internet including bundoomedscape, and others.  Most of the issues on this list are infections including paronychia, felon, and herpetic whitlow.  This matches my experience with patients.

Paronychia of the thumb.  Note the redness suggestive of infection.


One somewhat less common anomaly is the osteochondroma (bone and cartilage growth) from the distal phalanx which appears beneath the nail.  This so- called subungual (meaning literally beneath the nail) osteochondroma is benign meaning it does not spread and typically does not come back when removed surgically.  I have previously blogged a number of times about osteochondromas- typically in the setting of multiple osteochondromatosis, a hereditary condition with osteochondromas in numerous areas throughout the body- see posts HERE, HERE, HERE, and HERE.    Osteochondromas beneath the fingernails may be associated with multiple osteochondromatosis or can be isolated without any other lesion.

Patients with a subungual osteochondroma complain about several issues.  First, the patient notice a deformity of the nail.  The reason for this nail change is that the layer above the bone receives pressure from the growing osteochondroma and the nail matrix (or nail bed) is altered.  When the nail matrix is changed, the nail becomes abnormal.  The second complaint may be a visible deformity of the nail with a bump.  And lastly, there may be pain but this is not always the primary complaint.

Basic nail anatomy. Photo from Wikipedia.


Importantly, this diagnosis overlaps with the subungual exostosis as described on Wikipedia.  In short, subungual osteochondromas are one type of exostosis but not all exostoses are osteochondromas.  Importantly, while I primarily see and treat these in the fingers, they more commonly happen affecting the toenails.
Wikipedia pictures of big toe with subungual exostosis.


Here is a case of a subungual osteochondroma of the index finger causing nail irregularity and pain.  Surgical treatment involves nail removal, excision of the osteochondroma, and repair of the nailbed. The nail grows back over time.
Subungual osteochondroma causing nail irregularity

Subungual osteochondroma causing nail irregularity

Subungual osteochondroma causing nail irregularity

x-ray of subungual osteochondroma causing nail irregularity.  Note the bump on the top of the distal phalanx (beneath nail which is not visible on the xray).

x-ray of subungual osteochondroma causing nail irregularity.  The osteochondroma is more difficult to see here.

Charles A. Goldfarb, MD
My Bio at Washington University
congenitalhand@wudosis.wustl.edu

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