Entodermoscopy Update: A Contemporary Review on Dermoscopy of Cutaneous Infections and Infestations

Abstract

Infectious cutaneous diseases are very common, especially in certain geographic and tropical regions. Sometimes they may simulate other dermatoses, ordering verification of diagnosis with particular investigations. Dermoscopy is among one of the most important tools readily available in the outpatient setting for the dermatologist to confirm the diagnosis. In this up-to date review, literature concerning the various dermoscopic features of parasitic, viral, dermatophytic and bacterial cutaneous infections is composed. In addition artefacts as well as practical issues in dermoscopy usage are discussed; with the aim to empower dermatologists to promptly and non-invasively diagnose and manage cutaneous infections and infestations.

Keywords: Cutaneous infections; demodex; dermatophyte; dermatoscopy; dermoscopy; entodermoscopy; infestations; mite; molluscum; pediculosis; scabies; tinea; warts.

Figure 1

(a) When light is incident on the skin (thick red arrow), it gets reflected back (thin red arrow), while the remaining gets refracted (oblique orange arrow), diffracted (yellow shooting arrows) or absorbed (crimson area). On looking directly at the skin by unassisted eyes, one sees the external image of the skin formed by the reflected light; (b) Working principle of a modern dermoscope. In the polarized mode, the light gets polarized by two cross-polarizers, cutting out the scattered light reflected from the skin, allowing image formation with visualization of substratal structures

Figure 2

(a) In-vivo appearance of pediculosis capitis with nits in different stages of maturation/degeneration – active/viable (red circled) containing eggs closed with a tough porous operculum, non-viable nit with dead nymph or post-hatching of the nymph, with open operculum (light-blue circled), and empty nit with only air filled shell (yellow circled). Also appreciate 'pseudonits' most commonly seen as dandruff flakes (inside green rectangles), which are of bizarre-shape, and non-adherent to the hair shafts unlike the nits. [Heine Delta Dermoscope, non-polarizing, 20×]. (b) In-vivo high-magnification polarized videotrichoscopic images displaying nits in different stages of maturation/degeneration - (b) Active viable nit- ovoid brown colored structure containing viable embryo with intact operculum (black arrow).(c) Abortive Nit: translucent whitish-brown showing condensed non-viable embryo (yellow arrow) with surrounding air (white arrow). (d) Empty Nit: translucent crystalline-whitish colored open-ended nit without operculum after the discharge of the nymph or abortive embryo. [Dinolite premier AM4113 ZT videodermoscope, Taiwan, polarized, 80×]

Figure 3

Dermoscopic images of adult lice infesting humans: (a) Ex-vivo trichovideoscopic appearance of multiple mature head lice isolated from the patient's scalp that had heavy infestation. A maturing nymph can be seen (red arrow), which is relatively translucent compared to mature lice [Escope videodermoscope, polarized, 10×]. (b) Pubic region of an adult Indian patient showing a 'miniature-crab'-like light greyish-brown louse with six legs, clutching onto the firmly grasped pubic hair shafts with its foreleg-claws. [Escope videodermoscope, polarized, 10×]

Figure 4

(a) Low magnification (20×) polarized image of a scabetic burrow from the wrist of a young Indian lady showing a broad view of the delta wing with jet contrail sign. (b) Higher digital magnification (40×) polarized view showing the brown-colored triangular structure (enclosed within the black triangle) that resembles a delta-glider (inset), trailed by the jet contrail (confined by yellow lines). The jet contrail represents the burrow, and often shows whitish-yellow scales, and pigmented dark-brown colored granules and globules suggestive of the fecal pellets (light blue stars) [Heine Delta Dermoscope, polarized, non-contact

Figure 5

Higher magnification polarized videodermoscopy of scabetic burrows from two Indian children: (a) Appreciate the components of the delta wing jet contrail sign. A schematic diagram of 'jet contrail' can be seen in the inset for morphological comparison. Also appreciate the head, body, tail components of the new anatomo-functional concept called the Mite-Gallery Unit (MGU) proposed to broaden the concept that would consider different albeit related dermoscopic features as additional potential dermocopic clues for diagnosis of scabies with/without the classical clues. (b) In this image that also shows the typical sign as seen in (a), one can also observe the presence of few discreet pigmented structureless areas (white arrows) in the surrounding of the burrow, which is more commonly encountered in scabies patients who are dark-skinned, suggesting simultaneous and/or early development of post-inflammatory hyperpigmentation. [Escope videodermoscope, polarized, non-contact, 80×]

Figure 6

Clinicodermoscopic differentiation of Rosacea-like demodiciodosis (RLD) from papulopustular rosacea: (a) Clinical mage of the muzzle area of the face of a middle-aged lady with intolerance to photoexposure, off- and on itchy and scaly papular eruption over the muzzle area diagnosed with RLD. (b) Dermoscopy from the cheek revealed pinkish red background, with multiple demodex tails (black arrows), and demodex follicular openings (black asterisks). The blue circles have been drawn to surround comedones. Additionally, horizontally-to-haphazardly oriented reticular red dilated blood vessels can be seen, tending to form vascular polygons at places. But other features such as additional scale-crusts, follicular pustules are absent. (c) Facial image of a young lady suffering from chronic papulopustular rosacea with break through lesions. (d) Dermoscopy of the patient's cheek reveals dense erythema in the background, linear vessels characteristically arranged in a polygonal network (vascular polygons) follicular plugs, whitish-yellowish scales (black stars), orange-yellowish areas, pigmentation structures (black arrows), dilated follicles and follicular pustules (blue arrows), clues almost confirmatory of papulopustular rosacea [Escope videodermoscope, polarized, non-contact, 50×]

Figure 7

Cutaneous Larva Migrans (CLM) involving the dorsum of one foot in an adult Indian man: (a) Clinical image showing the burrows as raised, skin-to-tan- coloured discreet-to-coalescing linear, and curvilinear lesions (white arrows) with focal erythema and mild scaling. (b) Dermoscopy of the CLM lesions showing reddish-brown streaky thick lines (linear & curvilinear) and structureless areas in a segmental pattern (white arrows & arc) representing burrows with larva, and multiple red dotted-to-curved vessels (yellow crosses) scattered around these structures, i.e., remnants in the empty burrows. Additionally note the presence of focally present bizarre pigmented structures (light blue arrows) typical of darker skin types. [Escope videodermoscope, polarized, non-contact, 80×]

Figure 8

Bed Bug bites in a frequently travelling Indian businessman: (a) Clinical image showing multiple discreetly scattered maculopapules with central haemorrhagic punctum, and erythema-multiforme-like targetoid lesions over the back. (b) Dermoscopic observation (from the black circled region of image (a)) showing multiple haemorrhagic clodS (white arrows) signifying bite spots, and interspersed telangiectasias (white-colored + symbols) over a pinkish-background [Escope videodermoscope, polarized, non-contact, 150×]

Figure 9

Burrowing bug (Cydnidae) pigmentation: (a) Clinical image showing oval-to-lanceolate to bizarre-shaped pigmented macules scattered over the trunk and limbs of the affected adult. (b) Dermoscopy showing of cluster of numerous oval to shiny brown globules, granules, and bizarre-shaped pigmented structures that demonstrate a superficial “stuck-on” appearance and accentuation along the skin furrows and around the eccrine openings [Escope videodermoscope, polarized, non-contact, 80×]

Figure 10

Cutaneous Furuncular Myiasis (a) Clinical image of furuncular myiasis showing erythematous, indurated and tender furuncular nodules induration, over the trunk. Figure courtesy Yusuf et al[48]. (b) Dermoscopic image from another case of furuncular myiasis showing the posterior aspect of the larva. In the center, two bird's feet-like structures (white arrow) correspond to the breathing spiracles. At the periphery of the creamy-white larva, black dots are seen resembling a thorn crown (black arrow) [DermLite handheld II Hybrid dermoscope, polarized, 10×]; Figure courtesy Abraham et al[49]

Figure 11

Cutaneous Wound Myiasis: (a) Clinical image of wound myiasis showing well-circumscribed tender, boggy scalp ulcer with multiple larvae visible. Figure courtesy Gontijo and Bittencourt[52].(b) Dermoscopic image from the lesion showing numerous yellowish-white larvae with multiple brown dotted rings (green arrow), tracheal tube (blue arrow), and respiratory spiracle (red arrow). Erythema and perifollicular scaling on the scalp can be seen in the periphery. In the center, two bird's feet-like structures (white arrow) correspond to the breathing; Figure courtesy – Gontijo and Bittencourt[52]

Figure 12

Post-kala azar dermal leishmaniasis (PKDL): (a) Clinical image showing erythematous fleshy papules confined to the chin along with hypopigmented macules involving the trunk; Figures courtesy Jha et al[60]. (b) Dermoscopy of the erythematous papule from the chin revealed erythema, multiple yellow tears with few yellow clods (Dermlite II hybrid m dermoscope, polarized, 10×] [Figures courtesy Jha et al [60]]

Figure 13

Dermoscopic images of common warts with three different surface morphologies – (a) Raised verrucous surface of a common wart over the neck of an Indian man (appreciate the surrounding acanthosis nigricans) composed of papillary structures, each containing red dot/globule/loop and surrounded by a whitish halo giving a 'frogspawn' appearance (inset); additionally hemorrhagic crusts can be observed focally (yellow arrows) suggesting capillary thrombosis [Escope videodermoscope, polarized, non-contact, 50×]. (b) Florid cauliflower-like exophytic variant of common wart displaying all characteristic dermoscopic features including very densely packed papillae with red centres and whitish halo. Additionally, hemorrhagic crusts (yellow arrows) can be observed practically throughout the wart [Escope videodermoscope, polarized, non-contact, 80×]. (c) Filiform wart showing pink colored papillae with central linear and looped vessels. Also note the 'shriveled effect' produced by the disposable polythene cling film that was placed over the wart during dermoscopy to avoid cross-infection. [Dermlite II hybrid m dermoscope, polarized, 10×]

Figure 14

Plantar wart versus callosity: (a) Dermoscopy of a typical plantar wart showing the translucent yellowish-to-light brown packed papillary structures, interspersed with numerous hemorrhagic globules and streaks (yellow arrows). Also appreciate the complete disruption of the normal dermatoglyphics of the involved area of the sole (white broken arcs) by the viral invasion [Escope videodermoscope, polarized, non-contact, 50×]. (b) Higher magnification videodermoscopic view of an older and deeper plantar wart displaying plentiful and large hemorrhagic structures (yellow arrows), as well as streaks (blue arrows) in the periphery [Escope videodermoscope, polarized, non-contact, 150×]. (c) Dermoscopic image of a plantar callosity showing a homogenously opaque central translucent core and lack of vascularity. Appreciate the brownish-black 'pseudo-hemorrhagic structures' that are irregularly scattered (white arrows) and represent artifacts arising from dust and dirt [Dermlite II hybrid m dermoscope, polarized, 10×]. (d) Dermoscopic image of a post-cryoablation plantar wart, taken 2 weeks after the treatment session. Although yellowish-red structureless area can be appreciated, the dermatoglyphics are not as distorted, nor the centre of the lesion show the hemorrhagic crusts typical of an active wart [Escope videodermoscope, polarized, non-contact, 50×]

Figure 15

Dermoscopy of molluscum contagiosum showing central yellowish-white polylobular structure [Escope videodermoscope, polarized, non-contact, 50×]

Figure 16

Tinea cruris. (a) clinical picture showing erythematous scaly plaque in the groin. (b) Dermoscopic features suggesting fungal invasion of hair follicle (green arrows), diffuse erythema and scaling (yellow stars) and brownish pigmented blothches (orange star). (Dermlite DL3N 20X, polarized mode)

Figure 17

Tinea pedis, (a) Clinical picture depicting erythema and scaling pronounced over the web spaces. (b) Erythema and whitish scaling in the creases (yellow stars), broken hair (green arrow) (Dermlite DL3N 10X, polarized mode)

Figure 18

Tinea incognito. (a) Ill defined erythematous plaques with excoriations. (b) Translucent hair that looks weakened & shows bends (green arrows), erythema & mild scaling (yellow star), perifollicular scales and pustules (blue arrows) (Dermlite DL3N 20X, polarized mode)

Figure 19

Tinea capitis. (a) Clinical picture of localised patch of alopecia showing black dots and scaling. (b) Comma hairs (orange arrows), corkscrew hairs (yellow arrows), zig-zag hairs (green arrows). (Dermlite DL3N 10X, polarized mode)

Figure 20

Onychomycosis. (a) Jagged edge of the proximal margin of the onycholytic area (green lines), with sharp structure (spikes) directed to the proximal fold (blue arrows arrow), white- yellow longitudinal striae in the onycholytic nail plate (red arrows). (Dermlite DL3N 10X, polarized mode). (b) Fungal melanonychia: Dull matte black pigmented (red arrow) and yellow areas (green arrows) and pseudoleuconychia (yellow star). (Dermlite DL3N 10X, polarized mode)

Figure 21

Lupus vulgaris. (a) Clinically erythematous atrophic plaque with scarring extending from the left lower canthus to the cheek. (b) Dermoscopy revealing crimson-red to faint orangish background with yellowish structureless areas (black arrows), multiple linear branching vessels (white stars), and few whitish streaks (yellow diamonds). In addition, a pink scar surrounded by few brown to blue-grey pigmented globules and clods (green arrows) can be appreciated in the upper andcentral field. [DermLite II hybrid m; polarized, 10×]

Figure 22

Dermoscopy of hypopigmented macule of borderline Hansen's disease showing scattered dull-white structureless areas with accentuation along skin markings, reduced white dots of eccrine and follicular ostia, and a significant amount of residual pigment network visible [Dermlite 4, polarized, 10X]