Dr. Cohen is a dermatology resident at LECOM/Alta Dermatology in Mesa, Arizona. Email YC.
Keywords: scabies, dermoscopy, delta sign, triangle sign, diagnosis
Scabies is an itchy skin condition caused by a tiny burrowing mite called Sarcopetes scabiei. A scabies diagnosis can be confirmed by taking a skin scraping and seeing the scabies mite, scybala (its pellet-shaped feces), or ovum under the microscope. However, the traditional scabies preparations can be challenging to obtain in certain patient populations, such as young children. Dermatoscopy’s advantage is that it is non-invasive, painless and highly diagnostic in practiced hands. We would like to briefly discuss the typical dermatoscopic features that are seen in patients with scabies infestation.
The classic dermatoscopic features include “triangle sign”, which represents the “head” portion of the mite, and “the delta wing jet with contrail” signs, corresponding to the head of the mite and the trailing burrow. Confirmation of scabies by dermoscopy is less time consuming than traditional methods of identifying mites. At the minimum, dermoscopy enables the mites to be located, which allows traditional mineral oil scabies preparations to be targeted precisely.
The following image is taken from a burrow on the dorsum of hand of a teenage patient who had a few weeks history of intense itching. He presented with a generalized rash in the web spaces, flexural surface of wrists, feet and ankles. His abdomen, back and extremities were involved as well.
Figure 1. The red circle shows the triangular structure (delta wing jet), which indicates the head parts of scabies. The body of scabies is relatively translucent. There is a classic “S” shaped burrow above the triangular structure.
1. Fox G. Diagnosis of scabies by dermoscopy. BMJ Case Rep. 2009: 2009:bcr06.2008.0279
2. Argenziano G, Fabbrocini G, Delfino M. Epiluminescence microscopy. A new approach to in vivo detection of Sarcoptes scabiei. Arch Dermatol .1997; 133: 751–3
Dr. Cohen: “It is a great point and I’m always mindful of the contamination. I use an alcohol wipe between pts if there is no infectious potential, but definitely use a hospital strength disposable disinfectant wipe between pts if there is any possibility of infection. This was the same with my stethoscope between pts during internship. We must be careful. I would have the same expectation if I were a pt.”
from Dr. R. Shapiro: Dr. Cohen should add material to her note about either protecting the dermatoscope from getting contaminated in the first place with infectious agents by covering it with a plastic bag like a zip lock bag to prevent it from becoming a fomite, and/or how she carefully decontaminates it after using it ESP in this case