Gentian violet is an easy alternative to ultraviolet dermoscopy for the “ball sign” of scabies

PROBLEM

The ball sign is one of the new signs of scabies on ultraviolet (UV) dermoscopy. It refers to the demonstration of the body of the mite in addition to the mouthparts in UV dermoscopy as an oval bright white or greenish reflection.^[1] UV dermoscopy, a relatively recent innovation, combines a dermoscopy device with 365 nm UV illumination.^[2] It enhances the visualization of structures by filtering out the reflected fluorescence UV light. Despite the advantages of using UV dermoscopy, it is not as widely used as traditional dermoscopy because it is more expensive and has limited availability.^[3]

SOLUTION

To overcome this disadvantage, we used gentian violet dye, a simple yet easy alternative to UV dermoscopy. Gentian violet is applied over the suspected area with a cotton bud [Figure 1a and b]; after a few seconds, the area is cleaned with a spirit swab [Figure 1c] and examined under a conventional dermoscope in polarized mode [Figure 2]. The burrow and area surrounding the mite stain blue as gentian violet sweeps through, enhancing the body of the mite as an oval white structure shown with red arrow [Figure 2] with a brown triangle at the anterior part shown in yellow star (delta sign) [Video 1]. This helps to demonstrate not only burrows by dermoscope but also to confirm the presence of mites and burrow contents through a microscope [Figure 3a-c].

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Figure 1:

(a) Erythematous to hyperpigmented papulo nodular lesions on the left axilla of patient. (b) Gentian violet is applied on suspected area with a cotton bud. (c) Suspected area is wiped with spirit.

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Figure 2:

Dermoscopy (DL4, ×10 magnification, polarized mode) of burrow shows the body of the mite as white oval structure (ball sign – red arrow) and brown triangle (delta sign-yellow asterisk) corresponds to the anterior mouth parts after staining with gentian violet.

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Figure 3:

(a) Scabies mite examined under the microscope ×40, taken from scrapings. (b) Nymph seen under the microscope. (c) Egg of Sarcoptes scabiei.

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This simple and less time-consuming technique helps to visualize the “ball sign” of scabies with the help of a conventional dermoscope without upgrading to UV dermoscopy.