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General Instructions:

You will find a list of True/False statements following each case history. Select any statements, which you believe to be true. There may be one, more than one or no true statements for any given case. Choose the correct risk, diagnosis and disposition for each case. Then, turn the page to find a detailed discussion and pearls for each case.



A 75-year-old nursing home resident presents to the clinic with a 4-week history of an itchy rash on his trunk and extremities that is worse at night.

  1. The history and pityriasiform scaling are all that is needed to diagnose this contagious disease.

  2. Pinpoint and polymorphous vessels, pityriasiform scaling, and delta structures are the main features of this patient’s lichenoid drug reaction.

  3. Mineral oil scraping is a must, however, dermoscopy can also make a rapid diagnosis.

  4. A good eye is necessary to find primary lesions that should be examined with dermoscopy.

  5. Multiple curvilinear scaly areas, submillimeter, black, V-shaped bodies aka delta structures are seen here and make the diagnosis.


  • ☐ Pinpoint vessels

  • ☐ Polymorphous vessels

  • ☐ Delta structures

  • ☐ Curvilinear scaly areas

  • ☐ Bed bug skeletal structures


  • ☐ Drug reaction

  • ☐ Allergic contact dermatitis

  • ☐ Psoriasis

  • ☐ Bed bugs

  • ☐ Scabies


  • Linear burrows (dashed lines)

  • Delta bodies (arrows)

  • Pinpoint vessels (circles)


  • ☐ Drug reaction

  • ☐ Allergic contact dermatitis

  • ☐ Psoriasis

  • ☐ Bed bugs

  • ☑ Scabies


Answers: 3,4,5


  • The history, clinical, and dermoscopic appearance are all suggestive of scabies.

  • Now you must identify the scabies’ specific criteria.

  • The most obvious findings are the minute lines/burrows, which are unique to scabies.

  • The subtler finding, the triangular or V-shaped structures, corresponds to the head and the legs of the mite.

  • These are also referred to as “delta structures.”

  • V-shaped/delta structures are pathognomonic for scabies.

  • Skin scrapings with dermoscopy are superior to skin scrapings without dermoscopy (sensitivity 84% vs 47%).

  • Dermoscopy alone is as sensitive as skin scrapings.


  • It’s easier to try dermoscopy before skin scrapings to make the diagnosis.

  • Especially on small children that will be thrashing around!

  • Striking linearity seen with dermoscopy should be clues to an external etiology: factitial or infestation.

  • When classic dermoscopic features are present, skin scrapings are not necessary.

  • One’s goal is to find the delta structures.

  • They are often at the leading edge of each burrow (“delta wing bomber with contrail sign”).



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