Commentary

Although classically used for assisting the diagnosis of skin neoplasias, dermoscopy is increasingly gaining significant appreciation also in the field of general dermatology, including inflammatory, pigmentary, infectious, and infiltrative dermatoses [1]. Many articles on this topic have been published over the last few years, addressing common but also less frequent skin conditions whose recognition may be facilitated by dermoscopic examination [1]. Notably, several literature reviews have tried to summarize the possible indications of dermoscopy when it comes to the main non-neoplastic dermatoses, yet there is little awareness on the use of such a technique for rarer diseases [2,3,4,5,6]. To deal with such a gap, an in-depth search of the literature was performed to give an up-to-date temporal overview on all the non-neoplastic dermatoses whose dermoscopic features have been described, thus increasing the physicians’ awareness on the possible diagnostic uses of dermoscopy in general dermatology.

In detail, a search of the articles published up to 2020 was performed through the PubMed electronic database using the search terms “dermoscopy”, “dermatoscopy”, “videodermatoscopy”, or “epiluminescence microscopy”. Abstracts and titles were screened to identify papers describing dermoscopic findings of at least one inflammatory, pigmentary, infiltrative, or infectious skin disease (hair, nail, and mucosal conditions were not considered). A total of 6710 publications were analyzed and 305 different dermatoses (also including relevant disease variants characterized by dermoscopic peculiarities) with at least one dermoscopic description were identified. Figure 1 depicts the temporal distribution of the first dermoscopic report of such dermatoses, while Table 1 shows a complete list of the conditions according to the year of the first description.

Fig. 1
figure 1

Temporal distribution of the number of dermatoses whose dermoscopic features were described for the first time; dermoscopy of scabies and larva migrans were the first non-neoplastic dermatoses to be described (in 1997), while psoriasis, lichen planus, and pityriasis rosea were the first non-infectious conditions for which a dermoscopic report was available (in 2001)

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Table 1 List of non-neoplastic dermatoses whose dermoscopic features have been reported in the literature with the year of the first description
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This literature search highlights that the potential diagnostic applications of dermoscopy in non-neoplastic dermatoses are quite numerous. The initial reports in this field date back to 1997, when dermoscopic features of scabies and larva migrans were first described [7,8], while it was not until 2001 that findings of non-infectious inflammatory dermatoses start to be reported. Indeed, besides tinea nigra and nodular scabies, dermoscopic descriptions of psoriasis, lichen planus, and pityriasis rosea were published during that year. Afterwards, apart from a leap in the number of new dermoscopic reports of non-neoplastic dermatoses in 2004 as a result of the publication of an article describing the vascular structures seen in several conditions [9], few dermatoses were investigated from a dermoscopic point of view till 2008. Then a gradual increase took place over the time with the peak being observed in 2016, when dermoscopic features of a total of 42 new dermatoses were reported.

Importantly, more than 95% of the studies published on dermoscopy of non-neoplastic dermatoses have a low level of evidence (case reports/case series), with some of them revealing only poorly specific dermoscopic findings [1]. Nevertheless, if dermoscopic examination is used as the second step of a “two-step procedure”, after narrowing the differential diagnosis to two or few conditions on clinical grounds, less specific features may still come in handy as long as they reflect relevant histological differences [2]. For example, purpuric spots are considered unspecific by themselves but their presence may help distinguish urticaria vasculitis from urticaria as they are seen only in the former as a result of erythrocytes extravasation [6].

In conclusion, diagnostic applications of dermoscopy in general dermatology have become quite broad over the time and clinicians should be aware of dermatoses that may benefit from this technique because, if used with a systematic approach, it may significantly improve diagnostic accuracy of both common and less frequent conditions.