ORLANDO – In a patient presenting with a tender, firm lesion under the nail, think subungual exostosis, Dr. Phoebe Rich advised.
Subungual exostosis is a benign bony growth that can cause discomfort by pressing up from the nail bed. It can be mistaken for onychomycosis, but keep in mind that only 50% of those presenting with nail disorders will have onychomycosis, so it is important to consider other diagnoses, Dr. Rich, director of the Nail Disorder Center at Oregon Health and Science University, Portland, said at the Orlando Dermatology Aesthetic and Clinical Conference.
She described a teenager who presented with a growth under her nail, which the patient thought was nail fungus. The lesion developed after an injury experienced during a touch football game 2 months earlier.
An X-ray will aid in the diagnosis of such lesions, Dr. Rich said.
“You want to know that’s what it is … because you don’t want to just cut into it for a biopsy if you don’t know that it’s bone,” she said.
The diagnosis can be confirmed by removing the nail to take a look at the tumor.
“They are pretty characteristic. They are a bony growth. They’re actually composed of bone with a fibro-cartilaginous cap,” she said noting that tenderness is an important clue to the diagnosis.
Subungual exostosis occurs more often in toes than fingers, more often in girls than boys, and more often in children and young adults than older individuals, Dr. Rich noted.
Surgical removal is typically successful; the recurrence rate is about 10%, and recurrence is more common in children.
Presentation varies; some lesions can be quite obvious, with the growth protruding from under the nail, while others are more subtle. Dr. Rich described one young college student who presented with slight white spotting of the nail, and slight onycholysis. The patient had tenderness of the nail area when pressed, and the tumor peeked out from under the nail.
“If you see something like this, get an X-ray,” she said, adding: “You can be a hero and make the diagnosis. Don’t just treat it as though it’s a fungus.”
“If you’re very comfortable and expert at nails, great. Otherwise, make the diagnosis and send them to someone else, but you can really help these patients a lot,” she said.
Dr. Rich has participated in clinical trials with companies with antifungal/onychomycosis drugs, including Anacor, Merz, and Valeant.