Dermoscopy in General Dermatology: A Practical Overview
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Over the last few years, dermoscopy has been shown to be a useful tool in assisting the noninvasive diagnosis of various general dermatological disorders. In this article, we sought to provide an up-to-date practical overview on the use of dermoscopy in general dermatology by analysing the dermoscopic differential diagnosis of relatively common dermatological disorders grouped according to their clinical presentation, i.e. dermatoses presenting with erythematous-desquamative patches/plaques (plaque psoriasis, eczematous dermatitis, pityriasis rosea, mycosis fungoides and subacute cutaneous lupus erythematosus), papulosquamous/papulokeratotic dermatoses (lichen planus, pityriasis rosea, papulosquamous sarcoidosis, guttate psoriasis, pityriasis lichenoides chronica, classical pityriasis rubra pilaris, porokeratosis, lymphomatoid papulosis, papulosquamous chronic GVHD, parakeratosis variegata, Grover disease, Darier disease and BRAF-inhibitor-induced acantholytic dyskeratosis), facial inflammatory skin diseases (rosacea, seborrheic dermatitis, discoid lupus erythematosus, sarcoidosis, cutaneous leishmaniasis, lupus vulgaris, granuloma faciale and demodicidosis), acquired keratodermas (chronic hand eczema, palmar psoriasis, keratoderma due to mycosis fungoides, keratoderma resulting from pityriasis rubra pilaris, tinea manuum, palmar lichen planus and aquagenic palmar keratoderma), sclero-atrophic dermatoses (necrobiosis lipoidica, morphea and cutaneous lichen sclerosus), hypopigmented macular diseases (extragenital guttate lichen sclerosus, achromic pityriasis versicolor, guttate vitiligo, idiopathic guttate hypomelanosis, progressive macular hypomelanosis and postinflammatory hypopigmentations), hyperpigmented maculopapular diseases (pityriasis versicolor, lichen planus pigmentosus, Gougerot-Carteaud syndrome, Dowling-Degos disease, erythema ab igne, macular amyloidosis, lichen amyloidosus, friction melanosis, terra firma-forme dermatosis, urticaria pigmentosa and telangiectasia macularis eruptiva perstans), itchy papulonodular dermatoses (hypertrophic lichen planus, prurigo nodularis, nodular scabies and acquired perforating dermatosis), erythrodermas (due to psoriasis, atopic dermatitis, mycosis fungoides, pityriasis rubra pilaris and scabies), noninfectious balanitis (Zoon’s plasma cell balanitis, psoriatic balanitis, seborrheic dermatitis and non-specific balanitis) and erythroplasia of Queyrat, inflammatory cicatricial alopecias (scalp discoid lupus erythematosus, lichen planopilaris, frontal fibrosing alopecia and folliculitis decalvans), nonscarring alopecias (alopecia areata, trichotillomania, androgenetic alopecia and telogen effluvium) and scaling disorders of the scalp (tinea capitis, scalp psoriasis, seborrheic dermatitis and pityriasis amiantacea).
KeywordsDermatitis Dermatoscopy Dermoscopy Differential diagnosis Inflammoscopy Trichoscopy
Over the last few years, several studies have shown that dermoscopy may come in very handy for assisting the noninvasive diagnosis of various general dermatological disorders [1, 2, 3, 4, 5, 6], including scalp/hair diseases (trichoscopy) , nail/nailfold abnormalities (onychoscopy) , cutaneous infections/infestations (entomodermoscopy)  and inflammatory dermatoses (inflammoscopy) . Indeed, such a technique provides additional information at a submacroscopic level that may help the dermatologist differentiate between two or more conditions that are hardly distinguishable with the naked eye . The most important criteria to be considered when using dermoscopy in general dermatology are: (1) the morphology/arrangement of vascular structures, (2) scaling patterns, (3) colours, (4) follicular abnormalities and (5) specific features (clues) [1, 2]. Obviously, dermoscopic findings must be interpreted within the overall clinical context of the patient (personal/family history, number, location, morphology and distribution of the lesions, etc.) because only the combination between such data can really enhance the diagnostic accuracy in the field of general dermatological disorders [1, 2, 3, 4, 5, 6]. In fact, even though it has been demonstrated that some skin diseases may display “specific” dermoscopic criteria, there are others featuring just “nonspecific” findings, which may be considered useful only if coupled with proper and accurate clinical and anamnestic information [1, 2, 3, 4, 5, 6]. Another crucial factor that must be taken into account in dermoscopic examination of most dermatoses is the choice of the equipment [1, 2, 3, 4, 5, 6]. In particular, polarised light noncontact dermoscopy is usually preferred over conventional nonpolarised light contact dermoscopy as the latter may reduce the vessels (due to pressure) and/or scaling (when using a liquid interface) visibility, even though some clues are better seen with non-polarised light devices (i.e. more superficial findings, such as comedo-like structures) [1, 3].
The purpose of this article is to provide an up-to-date practical overview on the use of dermoscopy in general dermatology by analysing the dermoscopic differential diagnosis of several groups of relatively common dermatological disorders sharing the same (or similar) clinical presentation (erythematous-desquamative dermatoses, papulosquamous/papulokeratotic dermatoses, etc.) according to the available literature data and our personal experience. All published information about the dermoscopy of the conditions considered in the present article was retrieved by a comprehensive search of the literature using the PubMed electronic database (including all publications describing at least one instance); the search terms were the names of the diseases and the words “epiluminescence microscopy”, “dermatoscopy” and “dermoscopy”. A manual search was also carried out by analysing the reference sections of all relevant studies or reviews about such a topic.
For each clinical category, we will first describe the diseases for which there is good evidence (if any) and afterwards mention those having weaker evidence, specifying the highest level of evidence available for each considered dermatosis, according to the most recent guidelines for evidence-based medicine, The Oxford 2011 Levels of Evidence:  level of evidence I, systematic review of cross sectional studies with consistently applied reference standard and blinding; II, individual cross sectional studies with consistently applied reference standard and blinding; III, non-consecutive studies or studies without consistently applied reference standards; IV, case-control studies or “poor or non-independent reference standard”; V, mechanism-based reasoning. All the retrieved studies were classified according to standard definitions for diagnostic accuracy studies [10, 11, 12]. Importantly, blinded cross-sectional studies not mentioning the sampling method (consecutive or non-consecutive) were considered as non-consecutive studies (level of evidence III), while case series studies (CSS), single case reports (SCR) and personal observations (PO) were labelled as level of evidence V. To be more accurate, we will also specify the information source type (CSS, SCR and/or PO) in case the level V turns out to be the best evidence available.
Summary of the dermoscopic clues of all the dermatological disorders considered, divided according to their clinical pattern (Part I)
Dermatoses presenting with erythematous-desquamative patches plaques (I)
Dermatoses presenting with erythematous-desquamative patches plaques (II)
Papulosquamous—papulokeratotic dermatoses (I)
Papulosquamous—papulokeratotic dermatoses (II)
Dermoscopic clues of each dermatosis
• White scales
• Symmetrically and regularly distributed, dotted vessels on a light or dull red background
• Yellow serocrustsa
• Dotted vessels in a patchy distributionb
• Peripheral whitish scales (“collarette” sign)
• Irregular or patchy dotted vessels
• Orange-yellowish patchy areas
• Linear vessels with or without red dots forming peculiar “spermatozoon-like” structures
Subacute cutaneous lupus erythematosus:
• Whitish scale
• Mixed vascular pattern (at least two types among dotted, linear-irregular, linear and branching vessels)
• Wickham striae
• See “Facial inflammatory skin diseases (II)”
• See “Dermatoses presenting with erythematous-desquamative patches plaques (I)”
• Diffusely distributed dotted vessels
Pityriasis lichenoides chronica:
• Nondotted vessels
• Focally distributed dotted vessels
• Orange-yellowish structureless areas
Classic pityriasis rubra pilaris:
• Round/oval yellowish areas surrounded by linear dotted vessels
• Central keratin plugs
Summary of the dermoscopic clues of all the dermatological disorders considered, divided according to their clinical pattern (Part II)
Papulosquamous—papulokeratotic dermatoses (III)
Papulosquamous—papulokeratotic dermatoses (IV)
Facial inflammatory skin diseases (I)
Facial inflammatory skin diseases (II)
Dermoscopic clues of each dermatosis
Disseminated forms of porokeratosis:
• Peripheral “cornoid
• Diffuse tortuous irregular (or dotted at low magnification) vessels (early lesions)
• Central whitish-yellowish (hyperkeratotic lesions) or brown-grey (necrotic lesions) structureless area
Papulosquamous chronic GVHD:
• Whitish scales
• Dotted and linear vessels
Poikiloderma vasculare atrophicans:
• Sparse whitish scales
• Blurred branched vessels on a reddish/orangish background
Grover disease, Darier disease and BRAF-inhibitor-induced acantholytic dyskeratosis:
• Central star-shaped/branched polygonal/roundish-oval brownish area surrounded by a whitish haloa
• Linear vessels arranged in a polygonal network
• Dotted vessels in a patchy distribution
• Fine yellowish scales
Discoid lupus erythematosus:
• Perifollicular whitish halo (early lesions)
• Follicular keratotic plugs, red dots (early lesions)
• White scaling (early lesions)
• Whitish structureless areas (late lesions)
• Blurred linear branching (late lesions)
Sarcoidosis, cutaneous leishmaniasis and lupus vulgaris:
• Diffuse or localised, structureless, orange yellowish areas
• Focussed linear or branching vessels
• Dilated follicular openings
• Linear branching vessels
• “Demodex tails”b
• “Demodex follicular openings”b
Summary of the dermoscopic clues of all the dermatological disorders considered, divided according to their clinical pattern (Part III)
Acquired keratodermas (I)
Acquired keratodermas (II)
Hypopigmented macular diseases (I)
Dermoscopic clues of each dermatosis
• Diffuse white scaling
Chronic hand eczema:
• Brownish-orange dots/globules
• Yellowish scales/crusts
Keratoderma due to mycosis fungoides:
• Relatively large, amber scales over a white-to-pinkish background
Keratoderma due to pityriasis rubra pilaris:
• Patchily distributed, homogeneous, structureless, orange areas
• Whitish scales mainly localised in the creases
Palmar lichen planus:
• Roundish, yellowish
areas often having peripheral projections
Aquagenic palmar keratoderma:
• Yellowish-whitish well-defined globules
• Enlargement of the sweat duct pores
• Fibrotic beams
• “Comedo-like openings”
• Whitish patches
• Yellowish-orange/whitish-pinkish background
• Comma-shaped (incipient lesions), network-shaped/hairpin-like (more developed lesions), or elongated, branching and focussed serpentine (advanced lesions) vessels
Extragenital guttate lichen sclerosus:
• See “Sclero-atrophic dermatoses”
Achromic pityriasis versicolor:
• Fairly demarcated white area. Fine scales in the skin furrows
• Well-demarcated, dense/glowing, white area
• Perifollicular hyperpigmentation
Summary of the demioscopic clues of all the dermatological disorders considered, divided according to their clinical pattern (Part IV)
Hypopigmented macular diseases (II)
Hyperpigmented maculopapular diseases (I)
Hyperpigmented maculopapular diseases (II)
Hyperpigmented maculopapular diseases (III)
Dermoscopic clues of each dermatosis
Idiopathic guttate hypomelanosis:
• “Cloudy sky-like” or “cloudy” patterna
Progressive macular hypomelanosis:
• Ill-defined whitish area without scaling
• Dermoscopic findings typical of the original lesions
• Fine whitish scaling
• Pigmented network composed of brown stripes/diffuse brownish pigmentation
Lichen planus pigmentosus:
• Diffuse, structureless, brownish pigmentation
• Fine/coarse, grey-blue/brown dots/globules
Confluent and reticulated papillomatosis (Gougerot-Carteaud syndrome):
• Fine whitish scaling
• Brownish areas in a “cobblestone” or “sulci and gyri” pattern
• Brown star-like area/irregular brownish projections with a hypopigmented centre
Erythema ab igne (hyperpigmented stage):
• Diffuse brownish pigmentation
• Telangiectatic vessels
• Whitish scaling
Macular amyloidosis and lichen amyloidosus:
• White or brown central hub surrounded by various configurations of brownish pigmentationb
• Brownish structureless areas arranged in a reticular fashion
Terra firma-forme dermatosis:
• Large polygonal plate-like brown scales arranged in a mosaic pattern
• Homogeneous light-brown blot and/or pigment network
Telangiectasia macularis eruptiva perstans:
• Reticular vessels on a erythematous or brownish base
Summary of The dermoscopic clues of all the dermatological disorders considered, divided according to their clinical pattern (Part V)
Itchy papulonodular dermatoses
Noninfectious balanitis—erythroplasia of Queyrat
Dermoscopic clues of each dermatosis
Hypertrophic lichen planus:
• Rippled surface
• “Comedo-like” structures
• Round corneal structures (“corn pearls”)
• “White starburst” patterna
• Mites (“hang glider sign”)
• Burrows (“jet with condensation trails”)
Acquired perforating dermatosis:
• Three concentric areas with different aspect/colour
• Diffusely distributed whitish scales
• Regularly arranged dotted/glomerular vessels
Erythrodermic atopic dermatitis:
• Yellowish scales/sero crusts
• Patchily distributed dotted vessels
Erythrodermic mycosis fungoides:
• Linear vessels (including spermatozoon-like vessels) and dotted vessels
Erythrodermic pityriasis rubra pilaris:
• Orange blotches
• Islands of nonerythematous (spared) skin displaying reticular vessels
• Dark-brown triangular structures located at the end of whitish structureless wavy lines (delta-wing jets with contrail)
Zoon’s plasma cell balanitis:
• Focal/diffuse orange-yellowish structureless areas
• Fairly focussed curved vessels (including serpentine, convoluted and chalice-shaped)
• Regularly distributed dotted/glomerular vessels
Seborrheic dermatitis and non-specific balanitis:
• Linear irregular unspecific blurry vessels
Erythroplasia of Queyrat:
• Scattered glomerular vessels
Summary of the dermoscopic clues of all the dermatological disorders considered, divided according to their clinical pattern (Part VI)
Inflammatory cicatricial alopecia
Scaling disorders of the scalp
Dermoscopic clues of each dermatosis
Discoid lupus erythematosus:
• Follicular keratonc plugs, thick arborising vessels and red dots (acute lesions)
• Thin arborising vessels emerging from yellow dots (late lesions)
• White areas and branching vessels (long-lasting lesions)
• Perifollicular scales
Frontal fibrosing alopecia:
• Minor perifollicular scaling
• Lonely hair/predominance of follicular openings with only one hair at the hair-bearing margin
• Follicular pustules
• Yellow discharge/crusts
• Hair tufts that contain >10 hairs
• Black dots, micro-exclamation mark hairs, broken hairs, tapered hairs, monilethrix-like hairs and trichorrhexis nodosa (acute forms)
• Regular yellow dots (inactive lesions);
• Circle and/or pigtail hairs (regrowing phases)
• Hairs broken at different lengths
• Short hairs with trichoptilosis (“split ends”)
• Other: irregular coiled hairs, amorphous hair residues, black dots, flame-like hairs, tulip-like hairs and V-signa
• Hair shaft thickness heterogeneity
• Increased proportion of thin and vellus hairs (>10 % of the hairs)
• Lack of features typical of other diseasesb
• “Comma” hair, “corkscrew” hair, “zigzag” hair and “Morse code” hair
• Red dots/globules
• Signet ring vessels, red loops, white scales, punctate hemorrhages and hidden hairs (with a lower specificity)
• Arborizing vessels
• Yellowish scaling, structureless red areas, honeycomb pigment and comma vessels (with a lower specificity)
• Compact white keratotic material adhering to a tuft of hair (asbestos-like scale)
The article is based on previously conducted studies and does not contain any new studies with human or animal subjects performed by any of the authors.
Dermatoses Presenting with Erythematous-Desquamative Patches/Plaques
Plaque Psoriasis (Level of Evidence: II)
Eczematous Dermatitis (Level of Evidence: II)
The most important dermoscopic features of eczematous dermatitis include dotted vessels in a patchy distribution and yellow serocrusts/scaling (Fig. 1b) [13, 26, 27, 28]. Focal whitish scales are sometimes visible, but they are always associated with the aforementioned “yellowish findings” [13, 26, 27, 28]. According to the disease stage, eczematous dermatitis may display some differences, with acute exudative lesions mainly showing yellow scale/crusts (“yellow clod sign”) and chronic and lichenified lesions predominantly displaying dotted vessels in a patchy distribution and scaling [1, 13, 29, 30].
Pityriasis Rosea (Level of Evidence: II)
Both the herald patch and the secondary lesions of pityriasis rosea typically show a characteristic peripheral whitish scaling (“collarette” sign) as well as dotted vessels, which, differently from psoriasis, are distributed in an irregular or focal pattern; diffuse or localised yellowish-orange structureless areas may be visible as well (Fig. 1c) [13, 31, 32].
Mycosis Fungoides (Level of Evidence: III)
The most common dermoscopic aspect of mycosis fungoides consists of a combination of fine short linear vessels with orange-yellowish patchy areas (Fig. 1d) ; a peculiar vascular structure resembling spermatozoa (composed of a dotted and a short curved linear vessel) is also quite frequently visible . Additional dermoscopic features are represented by fine white scaling, dotted vessels and purpuric dots .
Subacute Cutaneous Lupus erythematosus (Level of Evidence: V—CSS)
Subacute cutaneous lupus erythematosus is characterised by two constant dermoscopic findings, namely whitish scales (diffusely or peripherally distributed) and a mixed vascular pattern (at least two types of vessels among dotted, linear-irregular, linear and branching vessels) over a pinkish-reddish background . Focally distributed orange-yellowish structureless areas may also be seen less commonly .
Classical Lichen Planus (Level of Evidence: II)
Pityriasis Rosea (Level of Evidence: II)
See the section “Dermatoses presenting with erythematous-desquamative patches/plaques”.
Papulosquamous Sarcoidosis (Level of Evidence: II)
Guttate Psoriasis (Level of Evidence: III)
Guttate psoriasis classically displays a distinctive monomorphic dermoscopic aspect consisting of dotted vessels regularly distributed all over the lesion, which are often associated with whitish scales (Fig. 2c) [1, 40], similarly to that seen in plaque-type psoriasis [1, 2, 3, 4, 5, 6, 41]; orange-yellowish structureless areas may also be present, but they are quite uncommon .
Pityriasis Lichenoides Chronica (Level of Evidence: III)
The most peculiar dermoscopic findings of pityriasis lichenoides chronica include nondotted vessels (i.e. milky red areas/globules, linear irregular and branching vessels), focally distributed dotted vessels and orange-yellowish structureless areas (Fig. 2d) . Interestingly, whitish areas may sometimes be present in the context of clinically active lesions as a result of focal post-inflammatory hypopigmentation [1, 40].
Classical Pityriasis Rubra Pilaris (Level of Evidence: V—CSS, CR)
Dermoscopy of classical pityriasis rubra pilaris papules may show round/oval yellowish areas surrounded by vessels of mixed morphology, namely linear and dotted [1, 16]. Additionally, central keratin plugs may also be observed .
Disseminated Forms of Porokeratosis (Level of Evidence: V—CSS, CR)
The most peculiar dermoscopic feature of all variants of porokeratosis is the “cornoid lamella”, which appears as a well-defined, thin, white-yellowish, annular peripheral hyperkeratotic structure (“white track”) similar to the outlines of a volcanic crater as observed from a high point, which may be hyperpigmented in disseminated superficial actinic porokeratosis (Fig. 2e); the centre of the lesions is usually whitish or brownish and may exhibit circular and/or linear whitish and/or hyperpigmented tracks, blue-grey dots and dotted, linear or globular vessels (Fig. 2e) [17, 42, 43, 44, 45, 46, 47, 48, 49].
Lymphomatoid Papulosis (Level of Evidence: V—CSS)
Dermoscopic pattern of lymphomatoid papulosis varies according to the disease stage. The initial inflammatory papules usually display a vascular pattern of tortuous irregular (or dotted at low magnification) vessels, surrounded by white structureless areas, radiating from the centre to the periphery of the lesion, while in more mature papules, such a vascular pattern is less evident and generally detectable only at the periphery of the lesion as the centre is occupied by a whitish-yellowish (hyperkeratotic lesions) or brown-grey (necrotic lesions) structureless area (Fig. 2f) .
Papulosquamous Chronic GVHD (Level of Evidence: V—CSS)
The dermoscopic aspect of papulosquamous chronic GVHD consists of whitish scales associated with vessels of mixed morphology, namely dotted and linear . Although such a pattern is quite unspecific, it might be useful in assisting the clinical differential diagnosis with the other above-mentioned papulosquamous disorders as they typically show a different appearance .
Poikiloderma Vasculare Atrophicans/Parakeratosis Variegata (Level of Evidence: V—CSS)
This condition typically shows a monomorphic pattern consisting of relatively blurred branched vessels on a reddish or orangish-brown background, associated with sparse whitish scales .
Acantholytic and Dyskeratotic Papular Disorders (Grover Disease, Darier Disease and BRAF-Inhibitor-Induced Acantholytic Dyskeratosis; Level of Evidence: V—CSS, CR)
Common Facial Inflammatory Skin Diseases
Rosacea (Level of Evidence: III)
Seborrheic Dermatitis (Level of Evidence: III)
The most typical dermoscopic findings of seborrheic dermatitis include dotted vessels in a patchy distribution and fine yellowish scales (in combination or not with white scales) (Fig. 4b); follicular plugs, orange-yellowish areas, whitish structureless areas and linear branching vessels are less common features .
Discoid Lupus erythematosus (Level of Evidence: III)
Dermoscopy of facial (and extra-scalp in general) discoid lupus erythematosus shows different features according to the stage of disease, with erythema, perifollicular whitish halo, follicular keratotic plugs, red dots and white scaling being the most common/characteristic features of early lesions, and whitish structureless areas, hyperpigmentation (honeycomb network, perifollicular pigmentation, radial pigment streaks or pigmentation arranged in unspecified pattern) and blurred telangiectasias (mainly linear branching vessels and less commonly dotted/polymorphous vessels) representing the most frequent findings of late phases [26, 61, 62, 63, 64, 65]; intermediate-stage lesions may display a mixture of the aforementioned features (Fig. 4c) [26, 61, 62, 63, 64, 65]. Less common dermoscopic findings include diffuse hyperkeratosis (hypertrophic discoid lupus erythematosus) , dilated follicles and yellowish scales [26, 61, 62, 63, 64, 65].
Granulomatous Skin Diseases (Sarcoidosis, Cutaneous Leishmaniasis and Lupus Vulgaris; Level of Evidence: III)
The dermoscopic signature of all these granulomatous facial dermatoses consists of structureless orange-yellowish areas (diffuse or localised—often described as “grains of sand” in lupus vulgaris and teardrop-like areas in leishmaniasis), commonly associated with focussed linear or branching vessels (Fig. 4d) [26, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80]. Other possible findings include milia-like cysts, erythema, whitish lines or structureless areas, follicular plugs, dilated follicles, pigmentation structures, and white and/or yellow scales [26, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80]. Additionally, leishmaniasis has been reported to show hyperkeratosis, further vascular features (hairpin, comma-shaped, glomerular-like and/or corkscrew vessels), central ulcerations and white peripheral projections (white starburst pattern) [73, 74, 75, 76, 77, 78, 79, 80]. Nevertheless, dermoscopy may not be considered as a reliable tool in differentiating such granulomatous diseases and therefore histological assessment is needed to reach a definitive diagnosis [26, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80].
Granuloma Faciale (Level of Evidence: III)
The dermoscopic hallmark of granuloma faciale is represented by the presence of dilated follicular openings associated with linear branching vessels (which sometimes appear as focussed elongated telangiectasias) over a pinkish background (Fig. 4e) [26, 81, 82, 83]; additional findings include perifollicular whitish halo, whitish streaks, follicular plugs, yellowish scales and pigmentation structures [26, 81, 82, 83].
Demodicidosis (Level of Evidence: V—CSS)
The most indicative dermoscopic features of all types of demodicidosis are the so-called "Demodex tails", which are creamy/whitish gelatinous threads (representing the presence of the mite itself under magnification) protruding out of follicular openings, and “Demodex follicular openings”, which appear as round and coarse follicular openings containing light brown/greyish plugs surrounded by an erythematous halo (Fig. 4f) . Other unspecific dermoscopic findings (whose prevalence varies according to the subtypes of demodicidosis) include diffuse erythema, scaling, pustules and reticular dilated vessels .
Chronic Hand Eczema (Level of Evidence: III)
Palmar Psoriasis (Level of Evidence: III)
The main dermoscopic finding of palmar psoriasis is represented by the presence of white scales typically distributed in a diffuse pattern (and only infrequently showing patchily or central distribution) (Fig. 5b) [23, 28, 85]. Dotted vessels, which are regularly distributed (and only rarely in rings or patchy-distributed), may also be visible quite commonly when using a fluid interface (which reduce the scaling) ; focal yellowish scales are an additional but very rare finding [23, 28].
Keratoderma due to Mycosis Fungoides (Level of Evidence: V—CR)
The most characteristic dermoscopic finding of keratoderma due to mycosis fungoides consists of relatively large amber scales over a white-to-pinkish background; sparse whitish scales and several non-specific reddish fissures are also visible .
Keratoderma due to Pityriasis Rubra Pilaris (Level of Evidence: V—CR)
The dermoscopic hallmark of keratoderma resulting from pityriasis rubra pilaris is the presence of patchily distributed, homogeneous, structureless orange areas presenting different sizes; unspecific whitish scaling may also be observed .
Tinea Manuum (Level of Evidence: V—PO)
From a dermoscopic point of view, tinea manuum displays whitish scaling distributed in a characteristic pattern, i.e. mainly localised in the physiologic palmar creases (Fig. 5c) (personal observations).
Palmar Lichen Planus (Level of Evidence: V—PO)
Palmar lichen planus is typically characterised by roundish yellowish areas often having peripheral projections that may create a star-like appearance; a purplish background is sometimes visible (Fig. 5d) (personal observations).
Aquagenic Palmar Keratoderma (Level of Evidence: V—CR)
Dermoscopy of aquagenic palmar keratoderma shows large yellow well-defined globules not affecting dermatoglyphs  or simply enlargement of the sweat duct pores when compared with a normal-looking palmar skin area [87, 88].
Necrobiosis Lipoidica (Level of Evidence: III)
Morphea (Level of Evidence: IV)
The most specific dermoscopic feature of morphea consists of whitish fibrotic beams, which are frequently crossed by linear branching vessels (Fig. 6b) [94, 95, 96]; pigment network-like structures are also often evident, while “comedo-like openings” and whitish patches are less commonly seen [94, 95, 96].
Cutaneous Lichen Sclerosus (Level of Evidence: IV)
The dermoscopic hallmarks of cutaneous lichen sclerosus include “comedo-like openings” (follicular keratotic plugs) and whitish patches (Fig. 6c) [94, 95, 97, 98, 99, 100]; less common/less specific findings are represented by delicate linear branching vessels, fibrotic beams, grey dots, purpuric spots, pigment network-like structures, non-branching vessels (comma-like, hairpin and/or dotted), fine whitish scaling and chrysalis structures [94, 95, 97, 98, 99, 100].
Hypopigmented Macular Diseases
Extragenital Guttate Lichen Sclerosus (Level of Evidence: IV)
See the section “Sclero-atrophic dermatoses”.
Achromic Pityriasis Versicolor (Level of Evidence: V—PO)
Guttate Vitiligo (Level of Evidence: V—CSS)
The most common/typical dermoscopic features of guttate vitiligo include a well-demarcated, dense/glowing, white area and perifollicular hyperpigmentation (which is more frequently seen in repigmenting or progressing lesions than stable lesions) (Fig. 7b) [102, 103, 104]. Other possible findings include perilesional hyperpigmentation, a reversed pigmentary network, reticular pigmentation and telangiectasias [102, 103, 104].
Idiopathic Guttate Hypomelanosis (Level of Evidence: V—CSS)
Dermoscopic examination of idiopathic guttate hypomelanosis displays two main aspects, i.e. the “cloudy sky-like” pattern (multiple small areas coalescing into irregular/polycyclic macules, with several white shades and both well- and ill-defined edges, surrounded by patchy hyperpigmented network) and the “cloudy” pattern (well or ill-defined roundish homogeneous whitish areas surrounded by patchy hyperpigmented network) (Fig. 7c) [101, 105].
Progressive Macular Hypomelanosis (Level of Evidence: V—PO)
Progressive macular hypomelanosis is dermoscopically characterised by an ill-defined whitish area without scaling .
Postinflammatory Hypopigmentation (Level of Evidence: V—CSS, PO)
Postinflammatory macular hypopigmentations often present some dermoscopic findings typical of the original lesions, e.g. non-dotted vessels/orangish structureless areas in pityriasis lichenoides [1, 40], dotted vessels in guttate psoriasis [1, 40] and star-like depigmentation in prurigo nodularis  (Fig. 7d), thereby assisting the retrospective diagnosis [1, 40, 106].
Hyperpigmented Maculopapular Diseases
Pityriasis Versicolor (Level of Evidence: V—CR, PO)
Lichen Planus Pigmentosus (Level of Evidence: V—CSS)
The main dermoscopic patterns of lichen planus pigmentosus are represented by a diffuse, structureless, brownish pigmentation and/or fine/coarse, grey-blue/brown dots/globules (Fig. 8b); perifollicular/annular pigmentation and white dots are other less common findings [38, 39, 108, 109].
Confluent and Reticulated Papillomatosis (Gougerot-Carteaud Syndrome; Level of Evidence: V—CSS, CR)
Confluent and reticulated papillomatosis typically displays fine whitish scaling associated with brownish, homogeneous, more or less defined, polygonal, flat globules separated by whitish/pale striae creating a cobblestone appearance  (Fig. 8c) or brownish areas presenting a “sulci and gyri” pattern .
Dowling-Degos Disease (Level of Evidence: V—CR)
Erythema Ab Igne (Hyperpigmented Stage; Level of Evidence: V—PO)
Primary Cutaneous Amyloidosis (Macular Amyloidosis and Lichen Amyloidosus; Level of Evidence: V—CSS)
The most common dermoscopic finding of both macular amyloidosis and lichen amyloidosus is a central hub (which is either white or brown in the former and white in the latter) surrounded by various configurations of brownish pigmentation, including fine radiating streaks, dots, leaf-like projections and bulbous projections . Additionally, in lichen amyloidosus the central hub may be replaced by a scar-like area (which may be the only feature in larger and thicker lesions) and a rim of white collarette (resembling a volcanic crater) may sometimes be appreciated .
Friction Melanosis (Level of Evidence: V—CR)
Terra Firma-Forme Dermatosis (Level of Evidence: V—CSS)
Dermoscopy of terra firma-forme dermatosis classically shows large polygonal plate-like brown scales arranged in a mosaic pattern .
Maculopapular Cutaneous Mastocytosis (Urticaria Pigmentosa, UP, and Telangiectasia Macularis Eruptiva Perstans, TMEP; Level of Evidence: V—CSS, CR)
The most common dermoscopic features of UP consist of a homogeneous light-brown blot and/or pigment network (Fig. 8f), while TMEP is mainly characterised by reticular vessels on an erythematous/brownish base (“reticular vascular” pattern), sometimes associated with a brownish network [117, 118, 119, 120, 121]. However, dermoscopy cannot guarantee a reliable distinction of such conditions as, albeit uncommonly, UP may display the reticular vascular pattern as well . Other less frequent vascular findings visible in both UP and TMEP include sparse dotted vessels and thin and tortuous linear vessels [117, 118, 119, 120, 121].
Itchy Papulonodular Dermatoses
Hypertrophic Lichen Planus (Level of Evidence: V—CR)
Prurigo Nodularis (Level of Evidence: V—CSS)
The dermoscopic hallmark of prurigo nodularis (both hyperkeratotic and excoriated lesions) is represented by the presence of the so-called “white starburst pattern”, consisting of radially arranged whitish lines or peripheral whitish halo with some centrifugal coarse projections on a brownish and/or reddish background, which may surround brown-reddish/brown-yellowish crust(s), erosion(s) and/or hyperkeratosis/scales (Fig. 9b) .
Nodular Scabies (Level of Evidence: V—CSS)
The distinctive dermoscopic sign of nodular lesions of scabies is the presence of mites (“hang glider sign”) and/or burrows (“jet with condensation trails”) . According to a recent study on ten patients with nodular scabies, the latter dermoscopic finding would be constantly present in such a type of scabies , but in our experience it may be missing (especially in extragenital sites) and unspecific vascular features (mainly dotted vessels) may be the only detectable findings (Fig. 9c) .
Acquired Perforating Dermatosis (Level of Evidence: V—CR)
The dermoscopic pattern of acquired perforating dermatosis is characterised by the presence of three concentric areas [1, 106, 124, 125], namely a central round brownish-greenish/yellowish-brown structureless area (I), surrounded by a white keratotic collarette (II) and an erythematous halo with or without dotted vessels (III) (“reactive perforating collagenosis” histological subtype) (Fig. 9d) [1, 106, 124] or bright white clods (I), centred in a structureless grey area (II), surrounded by reticular brown lines (III) (“perforating folliculitis” histological subtype) .
Erythrodermic Psoriasis (Level of Evidence: V—CR)
Dermoscopy of erythrodermic psoriasis reveals a monomorphous pattern with diffusely distributed whitish scales and regularly arranged dotted/glomerular vessels on a fairly homogeneous reddish background [29, 126].
Erythrodermic Atopic Dermatitis (Level of Evidence: V—CR)
As for other types of eczematous dermatitis, the most important dermoscopic features of erythrodermic atopic dermatitis consist of yellowish scales/serocrusts and patchily distributed dotted vessels on a pinkish background; unspecific sparse whitish scales may also be seen .
Erythrodermic Mycosis Fungoides (Level of Evidence: V—CR)
The most characteristic dermoscopic finding of erythrodermic mycosis fungoides is represented by the combination of linear vessels (some of them having a spermatozoon-like shape) and dotted vessels over a whitish-pinkish background; unspecific sparse whitish scales are also visible .
Erythrodermic Pityriasis Rubra Pilaris (Level of Evidence: V—CR)
Dermoscopy of erythrodermic pityriasis rubra pilaris typically displays peculiar orange blotches and islands of nonerythematous (spared) skin displaying reticular vessels; additional features include diffuse whitish scaling and scattered dotted vessels over a reddish background .
Erythrodermic Scabies (Level of Evidence: V—CR)
The main dermoscopic findings of erythrodermic scabies include whitish scales and thousands of characteristic dark-brown triangular structures located at the end of whitish structureless wavy lines (delta-wing jets with contrail) over a reddish background .
Common Forms of Noninfectious Balanitis and Erythroplasia of Queyrat
Zoon’s Plasma Cell Balanitis (Level of Evidence: V—CSS)
The dermoscopic hallmark of Zoon’s plasma cell balanitis is the presence of focal/diffuse orange-yellowish structureless areas and/or fairly focussed curved vessels (including serpentine, convoluted and chalice-shaped); other possible findings include linear irregular blurry vessels and dotted vessels .
Seborrheic Dermatitis and Non-Specific Balanitis (Level of Evidence: V—PO)
Seborrheic dermatitis and non-specific balanitis usually show only linear irregular unspecific blurry vessels .
Erythroplasia of Queyrat (Level of Evidence: V—CR)
Erythroplasia of Queyrat has been reported to show scattered glomerular vessels .
Common Inflammatory Cicatricial Alopecia
Discoid Lupus erythematosus (Level of Evidence: II)
Lichen Planopilaris (Level of Evidence: II)
The main dermoscopic features of active lichen planopilaris are perifollicular scales, which typically migrate along the hair shaft and form a tubular structure covering the proximal portion of the emerging hair shaft (“collar-like” or “tubular” perifollicular hyperkeratosis) (Fig. 10d) [132, 133, 136, 137, 138, 139, 140, 141, 149, 150]; other possible dermoscopic findings of active lesions include violaceous or violet-brown inter- or perifollicular violaceous areas (Fig. 10d), perifollicular inflammation, elongated linear blood vessels in concentric arrangement and target “blue-grey dots” [132, 133, 136, 137, 138, 139, 140, 141, 149, 150]. Inactive/late lesions may show characteristic (but not pathognomonic) irregular, large white dots (fibrotic white dots) (Fig. 10d) as well as less specific findings such as acquired pili torti, loss of follicular openings, white areas, honeycomb/scattered hyperpigmentation, milky red areas (strawberry ice cream colour) and small hair tufts of 5–9 hairs [132, 133, 136, 137, 138, 139, 140, 141, 149, 150].
Frontal Fibrosing Alopecia (Level of Evidence: II)
The most common dermoscopic findings in frontal fibrosing alopecia include a lack of follicular openings and minor perifollicular scaling [131, 132, 137, 140, 141, 142, 143, 144]; additionally, perifollicular erythema may be seen but the surrounding background is usually aflegmasic (ivory white to ivory beige) (Fig. 10e) [131, 132, 137, 140, 141, 142, 143, 144]. Interestingly, there is often a strong predominance of follicular openings with only one hair at the hair-bearing margin and lonely hair may be observed (Fig. 10e) [131, 132, 137, 140, 141, 142, 143, 144]. Fine arborising vessels and perifollicular brown or brown-violet areas may sometimes be visible [131, 132, 137, 140, 141, 142, 143, 144].
Folliculitis Decalvans (Level of Evidence: II)
The most characteristic dermoscopic feature of folliculitis decalvans is the presence of hair tufts that contain >10 hair shafts (Fig. 10f), which are often surrounded by a band of yellowish scales (yellowish tubular scaling) and by perifollicular epidermal hyperplasia (which may be arranged in a starburst pattern) at their base [132, 133, 137, 145, 146, 147, 148]; other peculiar findings in active folliculitis decalvans include follicular pustules and yellow discharge and crusts (Fig. 10f) [132, 133, 137, 145, 146, 147, 148, 149]. A perifollicular concentration of blood vessels (elongated loops/coiled vessels) and a perifollicular erythema arranged in a starburst pattern may also be visible [132, 133, 137, 145, 146, 147, 149]. In long-lasting lesions, ivory-white and milky-red areas without follicular orifices predominate .
Common Nonscarring Alopecias
Alopecia Areata (Level of Evidence: II)
Trichotillomania (Level of Evidence: II)
Dermoscopy of trichotillomania often reveals a chaotic pattern of diverse findings related to hair fracturing [151, 159]. The most peculiar features include hairs broken at different lengths, short hairs with trichoptilosis (“split ends”), irregular coiled hairs, amorphous hair residues, black dots, flame-like hairs, tulip-like hairs (short hairs with darker, tulip-shaped ends) and V-sign (two or more hairs emerging from one follicular unit that are broken at the same level) (Fig. 11b) [131, 139, 151, 156, 159, 160, 161, 162, 163]. Less common/less specific findings are tapered hairs, follicular microhemorrhages, micro-exclamation mark hairs and upright regrowing hairs [151, 159, 160, 161, 162, 163].
Androgenetic Alopecia (Level of Evidence: IV)
The main dermoscopic features of androgenetic alopecia include hair shaft thickness heterogeneity, yellow dots (irregularly distributed and with a remarkable variability in size and shape), perifollicular discolouration (the peripilar sign), an increased proportion of thin and vellus hairs (>10 % of the hairs) and a large number of follicular units with only one emerging hair shaft (Fig. 11c) [131, 132, 139, 164, 165, 166, 167, 168]. Thin wavy hair and honeycomb hyperpigmentation often coexist as additional, nonspecific features (Fig. 11c) [131, 132, 139, 164, 165, 166, 167, 168].
Telogen Effluvium (Level of Evidence: IV)
The most indicative dermoscopic clue of telogen effluvium is the lack of features typical of other diseases (Fig. 11d) [131, 139, 169]; common, but nonspecific, findings include the presence of empty hair follicles, a predominance of follicular units with only one hair, perifollicular discolouration (the peripilar sign), upright regrowing hairs (mainly acute forms) and progressive uniform hair thinning (chronic forms) (Fig. 11d) [131, 139, 169]. There is no significant difference between the findings in the frontal area and those in the occipital area, which differentiates telogen effluvium from androgenetic alopecia; however, it is important to underline that both disorders may coexist [131, 139, 169].
Common Scaling Disorders of the Scalp
Tinea Capitis (Level of Evidence: II)
The main dermatoscopic features of tinea capitis are represented by “comma” hair (c-shaped hair shaft with a sharp, slanting end and homogeneous thickness), “corkscrew” hair (twisted or coiled, short, broken hair fragments), “zigzag” hair (hair shaft bent at multiple points) and “Morse code” hair [presence of multiple transverse bands (gaps) throughout the hair shaft] (Fig. 12a) [151, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187]. Other nonspecific trichoscopic findings in TC include broken and dystrophic hairs, i-hair, black dots, yellowish dots, erythema, scaling, pustules, elongated blood vessels, tufted hair and large yellowish wax-coloured perifollicular areas (favus) [151, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187].
Scalp Psoriasis (Level of Evidence: III)
Seborrheic Dermatitis (Level of Evidence: III)
The most characteristic dermoscopic findings of seborrheic dermatitis of the scalp consist of arborising vessels [138, 188, 189, 190]; additional indicative features are yellowish scaling, featureless areas (structureless red areas), honeycomb pigment and comma vessels (Fig. 12c) [138, 188, 189, 190]. Less specific finding include other vascular structures, pigmentations (perifollicular pigmentation, honeycomb pigment pattern and brown dots) and white/yellow dots [138, 188, 189, 190].
Pityriasis Amiantacea (Level of Evidence: V—CR)
Dermoscopy may be a helpful auxiliary tool in assisting the the noninvasive recognition/differential diagnosis of several “general” dermatoses by magnifying both surface structures and subsurface features that are invisible to the unaided eye and reflect the different histopathological background of each condition. Importantly, this article should be read with a critical eye as it presents three limitations: (1) the comparative analysis of several dermatoses is not the result of direct comparative studies but has been made merely considering the dermoscopic appearance of each condition; (2) the dermoscopic description of some considered diseases is based on limited observations; (3) the level of evidence assigned to each dermatosis is based on the study/studies showing the best evidence available, so some of the reported dermoscopic findings might come from works with a lower level of evidence. Of note, in this analysis, we also considered studies lacking strong evidence as there is a growing recognition that observational studies (even case series, case reports and anecdotes) may provide worthy information, especially if they are properly supported by mechanism-based reasoning (e.g. dermoscopic-pathological correlations) [192, 193, 194]. Anyway, further high-quality, prospective, blinded, controlled investigations are needed to better characterise the use of dermoscopy in general dermatology.
We are extremely grateful to Dr. Angelo Piccirillo for providing us with Fig. 4d and Prof. Pasquale Patrone for the outstanding encouragement to write this article. No funding or sponsorship was received for this study or publication of this article. All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this manuscript, take responsibility for the integrity of the work as a whole and have given final approval for the version to be published.
Enzo Errichetti and Giuseppe Stinco declare no conflict of interest.
Compliance with Ethics Guidelines
The article is based on previously conducted studies and does not contain any new studies with human or animal subjects performed by any of the authors.
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