<p>A 67 year old was referred with a slowly evolving single black toenail. On examination there was marked thickening under the nail (subungual hyperkeratosis) suggesting the likely aetiology of a fungal infection. </p>
<p>Although most nail fungal infections are white/yellow, just occasionally they can appear black. </p>
<p>In order to prevent high rates of false negative results it is important to the cut the nail back and remove the subungual debris by careful curettage or by using a scalpel blade, and send all of the specimen for mycology. <strong>Simply asking the patient to provide a nail clipping will miss many cases of fungal infection.</strong></p>
<p>Mycology confirmed the presence of tinea rubrum.<span></span></p>
<p>Images copied with kind permission from South Tees Hospitals NHS Foundation Trust.</p>
