The Usefulness of Dermoscopy for Detection of Subungual White Foreign Bodies.

Dear Editor:

Dermoscopy is a noninvasive and extremely useful diagnostic tool for a variety of skin diseases1. A few reports have documented that dermoscopy is also useful for the diagnosis of some zoonotic infestations including scabies and spider spines23. In the latter, dermoscopic findings allow the identification of spider spines clinically mimicking scabies. Here, we report a case of the successful identification and removal of a fish bone under the fingernail with the aid of dermoscopy.

A 51-year-old woman presented with a 7-day history of pain in the right thumb. She had trimmed a black rockfish caught by her husband, and felt pain afterwards. When she came to our department after failing to remove the bone herself, it was difficult to find the fish bone with the naked eye (Fig. 1A). However, we were able to find a linear foreign body embedded under the nail plate using dermoscopy (Fig. 1B). The foreign body was easily removed using fine forceps.

Fig. 1

(A) It was difficult to locate the foreign body with the naked eye. (B) Dermoscopic findings revealed the foreign body to be compatible with a fish bone spine and focal abscess pocket.

Having the fingers pricked by a fish bone or thorn is not uncommon. Sometimes the removal of these foreign bodies can be difficult, and persistently disabling secondary infections can occur in cases of residual fragments4. However, it is often difficult to detect subungual white foreign bodies like fish bones and white hairs with the naked eye. Imaging approaches including routine X-ray, computed tomography, and magnetic resonance imaging can be helpful, but seem too extreme considering their expense and limited availability5. Using dermoscopy, we were able to identify the exact location of the colorless foreign body under the nail plate and remove it easily.

In conclusion, dermoscopy can be a useful diagnostic tool for the detection of white foreign bodies such as fish bones in the subungual space.