A 34-year-old man is seen in a clinic for evaluation of severe nocturnal itching and rash on the wrists and waist. He denies any other symptoms. Examination of his hands reveals burrows on the flexor surfaces and interdigital spaces. A clinical diagnosis of scabies is made.
Which one of the following is the best method to make a definitive diagnosis of scabies?
Figure 1. Adult Male and Female Sarcoptes scabiei Mites
Image of adult male (left) and female (right) Sarcoptes scabiei. Note the larger size of the adult female.
Illustration: Cognition Studio, Inc. and David H. Spach, MD
Figure 2. Sarcoptes scabiei Life Cycle
The lifecycle of Sarcoptes scabiei is 30 to 60 days and is completed entirely in humans. Females burrow through the stratum corneum of the epidermis and lay 10 to 25 eggs at the end of the burrowed tunnels. The eggs hatch after 3 to 4 days, and larvae mature to adults on the skin.
Source: Currie BJ, McCarthy JS. Permethrin and ivermectin for scabies. N Engl J Med. 2010;362:717-25.
Reproduced with permission. Massachusetts Medical Society. ©2010.
Figure 3. Scabies Hot Spots of Cutaneous Involvement
Common sites of Sarcoptes scabiei infestation include the hands, wrists, elbows, axillae, groin and umbilical region, as shown in the anterior and posterior view of adult human.
Illustration: Cognition Studio, Inc. and David H. Spach, MD
Figure 4. Scabies Burrow
This image shows effect of burrowing on skin created by a pregnant female mite that has tunneled into the epidermis to lay eggs. Burrows can be up to 1 cm in length and on examination have a black dot at the end, which represents larvae, eggs, or feces. Inside the burrow, there are eggs and a female mite.
Illustration: Cognition Studio, Inc. and David H. Spach, MD
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Question Last Updated
March 13th, 2025
March 13th, 2025
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