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General Instructions

  • For each case, there is a short history along with a clinical and an unmarked dermoscopic image.

  • Study the unmarked dermoscopic image and try to identify the global and local dermoscopic features.

  • Make your diagnosis.

  • Next, turn the page and the dermoscopic image will be presented again, this time marked with all the salient dermoscopic findings.

  • On the same page you will also find the diagnosis along with a detailed discussion and a few pearls for your review.



These lesions were symmetrically located on the shins of a 70-year-old woman.


  • Peripheral white to brownish scaly rim (“white track”) (red arrows)

  • Double white track at some sites of the peripheral rim (black arrows)

  • Multiple dotted/pinpoint (black stars) and a few short linear vessels (black circle)

  • Homogeneous white-yellowish center in 2 lesions (yellow stars)


Disseminated Superficial Actinic Porokeratosis


  • The diagnosis is disseminated superficial actinic porokeratosis.

  • The dermoscopic hallmark of disseminated superficial actinic porokeratosis is white track structures at the periphery.

    • These structures have also been described as “volcanic craters.”

    • They may be singular or double.

    • They reflect the pathognomonic cornoid lamellae of disseminated superficial actinic porokeratosis seen on histopathology.

  • Red dots, globules, and lines in the center correspond to the vessels of the superficial plexus that become visible as a result of the central atrophy typical of disseminated superficial actinic porokeratosis.

  • White-yellowish homogeneous areas that correspond to acanthosis are rarely seen.

  • Depending on the clinical subtype of porokeratosis, different dermoscopic features may be seen.

    • For example, porokeratosis of Mibelli is characterized by dark brown continuous lines circumscribing a central hypopigmented scar-like area. Brown globules/dots and red dots in the central area may also be found.


  • The peripheral white track structure in dermoscopy is a strong diagnostic criterion of any type of porokeratosis, because it is never seen in other dermatologic entities.



A 79-year-old man complained of swelling, redness, and itching on his face for the past year.


  • Linear vessels arranged in a polygonal network (black circles)

  • Spiny white threads protruding out of the follicular openings (Demodex “tails”), corresponding to Demodex folliculorum (black arrows)

  • White-yellowish globules, corresponding to pustules (yellow arrows)

  • White scales (black star)


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