Utility of a Multispectral Dermatoscope in onychomycosis.

Sir,

Nail plate dermatoscopy is a simple, quick and quite helpful technique in the diagnosis and follow-up of onychomycosis.[1] Dermatoscopy has also been used to identify the best location in the nail plate to obtain samples for mycological examination. The dermatoscopic findings that are considered specific for onychomycosis include jagged proximal edge of onycholysis with sharp structures called spikes directed to the proximal nail fold, white-to-yellow longitudinal striae, and parallel bands of different colours called the “Aurora Borealis” pattern.[2] Jagged proximal edge is due to progression of dermatophytes proximally along longitudinal ridges of the nail bed.[3] However, a thick nail plate [Figure 1] can obscure deeper dermatoscopic findings of longitudinal striae and jagged proximal edge when examined with a routine white light dermatoscope [Figure 2].

Figure 1

Onychomycotic thick nail plate viewed from front with white light dermatoscopy (×10)

Figure 2

White light dermatoscopy showing spikes (short arrow) and longitudinal striae (black arrow) (×10)

We used a multispectral dermatoscope which gives a 10x magnification (DermLite DL II Multispectral, 3Gen Inc., USA) which emits light at three wavelengths, namely, 470 nm, 580 nm and 660 nm corresponding to blue, yellow and red colours, respectively, to examine this case of onychomycosis confirmed with KOH microscopic examination. Images were captured using Nikon1 AW1 14.1 MP mirrorless camera (Nikon Corp., Tokyo, Japan) and ultrasound gel was used as interface fluid. Light penetrates deeper into the tissues as the wavelength increases.[4] Depending on the tissue, light penetrates <1 mm at 400 nm, up to 2 mm at 514 nm, and up to 6 mm at 630 nm.[5]

In our case, though spikes and white longitudinal striae are seen with white light, the delineation was better with yellow light (580 nm) as the light penetrates deeper to highlight the nail bed features excluding the superficial distractors seen with white light [Figure 3]. The same may vary with different thicknesses of the nail plate. We advocate larger studies in the future to highlight this concept of differences in light penetration based on thickness of the nail plate. Hence, a multispectral dermatoscope is useful for better dermatoscopy of onychomycosis, especially in thicker nails.

Figure 3

Yellow light (580 nm) delineating features of onychomycosis-spikes (short arrow) and longitudinal striae (black arrow) in a better fashion (×10)

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understood that his name and initial will not be published and due efforts will be given to conceal his identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.