Porokeratosis Differential Diagnoses

Updated: Oct 09, 2020
  • Author: Amarateedha Prak LeCourt, MD; Chief Editor: William D James, MD  more...
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Diagnostic Considerations

Dermoscopy shows a "white track" structure at the periphery of the lesion, corresponding to the cornoid lamella. Occasionally the white track may be a double white track, with brownish discoloration within the furrow, especially in larger lesions such as porokeratosis of Mibelli (PM). The center may show a white homogeneous area, corresponding to an atrophic epithelium. Red dots, globules, and lines corresponding to enlarged capillary vessels that can be seen through the atrophic epithelium. [69]

The dermatoscopic features of the cornoid lamella can be accentuated using marker ink. This also highlights the presence of hair follicles and acrosyringia, some with keratotic plugs. [70]

In terms of modalities to visualize a cornoid lamellae, incisional biopsy perpendicular to the border is preferred over punch biopsy as one may lose the coronoid lamellae during processing of the punch biopsy specimen. [1]

However, a 2016 article illustrates a new biopsy technique that allows for proper orientation of the specimen during processing of PM. The authors propose a three-step technique: (1) draw a line perpendicular to the rim of the lesions, (2) then perform a punch centered at the intersection of the drawn line and coronoid lamellae, (3) then section along the perpendicular line. The laboratory acquisition should mention transection, and the cut sides should be placed down when processed. [71]

Differential Diagnoses