The modern mobile phone is both loathed and liked – particularly because of the large amount of time people spend glued to it over the course of the day but novel uses are always welcome, particularly if they can be helpful in making a serious dermatological diagnosis! In a forthcoming short paper to be published in the Journal of the American Academy of Dermatology, Chelidze and colleagues describe the infamous “selfie” as a useful tool to help discriminate a sub-ungual haematoma from a sub-ungual melanoma presenting as a melanonychia.
The process is quite simple, the patient is instructed to write the date on a clean piece of unlined paper then place the offending toe (or finger) onto the centre of the paper. Along the lateral edge of the toe, perpendicular to the cuticle, they place a ruler and take a picture. The patient is instructed to do this on a regular basis until they return to clinic within a few weeks. At the appointment the patient is then able to present a serial sequence of images which can help decide if the lesion is growing out or progressing. Obviously, haematoma will begin to clear the proximal edge (unless the toe is being repeatedly traumatised) whilst a melanoma will continue to emerge but also evolve with signs such as widening, darkening or spreading onto the peri-ungual tissues (Hutchinson's sign) .
Black-brown sub-ungual discolouration of the nail, emanating from under the proximal nail fold, is always a cause for concern in terms of making a differential diagnosis but thankfully, haematoma is far more common diagnosis than nail melanoma. Even so, careful investigation is required where there is doubt. A history and thorough assessment is always required. A nail biopsy (which can be painful, complicated or lead to permanent nail changes) could be sought but the toe selfie is a less invasive method as the authors suggest.
The advantages of course, are obvious, not only is it a lower risk procedure but it also helps to get the patient involved and take charge of their care, which can be particularly helpful when they are anxious. Of course, to do this you would need a type of phone which has a camera capable of close range focus (macro setting) but most current phones have that function built in.
If there is any doubt about a diagnosis of melanonychia, a referral to a dermatologist is always recommended.
Reference
Chelidze, K., D. Ko and S. R. Lipner (2017). "The Nail Hematoma Selfie." Journal of the American Academy of Dermatology. Accepted and awaiting publication
For more information on recognising a nail melanoma, please see the guidelines published on this subject by clicking here.