Pigmented purpuric dermatoses versus purpuric mycosis fungoides: Clinicopathologic similarities and new insights into dermoscopic features.

Background: The diagnosis of purpuric mycosis fungoides (PMF) is often challenging to be clinically differentiated from inflammatory diseases such as pigmented purpuric dermatosis (PPD). Dermoscopy as a non-invasive method can be employed for the visualisation of features invisible to the naked eye.
Objectives: This study aimed to survey the dermoscopic findings of PMF in comparison with PPD.
Methods: Forty-one patients with an established diagnosis of PMF (n = 28) and PPD (n = 13) were prospectively recruited. Dermoscopic images were taken by FotoFinder Medicam 1000 (FotoFinder Systems GmbH, Bad Birnbach, Germany).
Results: Characteristic dermoscopic patterns consisting of fine short linear vessels (35.7%, P = 0.017) and spermatozoa-like structures (50%, P = 0.014) were found to be significantly more common in PMF lesions, while PPD lesions were typified by erythematous globules (76.9%, P = 0.01), in the background colour of dull red (61.5%, P = 0.01) and reticular pigmentation (61.5%, P = 0.044).
Conclusions: This study showed the usefulness of dermoscopy for the diagnosis of PMF and PPD cases. Studies with long-term follow-up are needed to affirm the value of these dermoscopic patterns in the differentiation between the two entities.
(© 2021 The Australasian College of Dermatologists.)