Dermoscopic Evaluation of Inflammatory Nail Disorders and Their Mimics

Abstract

Nail dermoscopy (onychoscopy) is a valuable diagnostic tool for evaluating diseases in the nail apparatus. It is non-invasive, allowing clinicians to prioritize particular nails for biopsy. Thus, it can improve diagnostic accuracy and expedite treatment. Evaluating inflammatory nail disorders using onychoscopy is a relatively new approach to clinical assessment and has the potential to augment clinical care. This review highlights key dermoscopic features of major inflammatory nail disorders, including trachyonychia, nail psoriasis, nail lichen planus, onychotillomania, nail lichen striatus and allergic contact dermatitis due to artificial nails. It also illustrates their management and differential diagnoses, including onychomycosis, onycholysis, nail dystrophy due to systemic amyloidosis and malignant nail tumours. Limitations of this review included the low amount of literature on this topic and non-standardized terminology used among researchers. As onychoscopy is a relatively new technique, further studies and standardization of terminology are warranted to consolidate the role of dermoscopy in evaluating inflammatory nail disorders.

Diagnosing Onychomycosis: What’s New?

“…Dermoscopy, also called onychoscopy, provides non-invasive observation of the epidermis, dermal papilla, and deep dermis by eliminating reflected light through polarized photography [ 21 , 22 ]. Characteristic dermoscopic features of onychomycosis include spikes, longitudinal striae, subungual hyperkeratosis, and color changes [ 23 ] ( Figure 1 D). Handheld dermoscopy visualization is fast and low-cost [ 24 ].…”

“…The technique does have a limited depth of penetration, varying based on scanning laser wavelength, and only moderate levels of sensitivity and specificity have been reported [ 10 , 36 , 37 ]. Confocal microscopy can provide direct imaging of fungal structures suggestive of onychomycosis, showing as bright filamentous septate hyphae [ 23 , 33 ] ( Figure 1 F). Devices report use of RCM (830-nm), infrared CLSM (1064-nm) and dual wavelength RCM/CLSM (488-nm and 785-nm) for onychomycosis visualization [ 3 , 33 , 38 ].…”

Pattern diagnosis of onycholysis

“…7,16 These forces cause greater impact on the central area of the nail than on the lateral nail folds; leukonychia and capillary dilatation proximal to the onychodermal band may ensue, and intense trauma may cause splinter haemorrhage. 16 In the toenails, gait anomalies, long toenails, and inappropriate shoes are associated with traumatic linear transversal onycholysis, usually bilateral and symmetrical; the nails show a white or yellowish (due to nail thickening) colour, and on dermoscopy the proximal margin of onycholysis is sharp and linear [17][18][19] (Figure 5). A pathway mimicking the EKG atrial fibrillation pattern in the distal margin is another feature supporting a traumatic origin.…”

“…37 The distal onycholytic area has a silvery whitish hue that is more pronounced in the lateral zones of the nail and looks different to the yellowish-white colour in onychomycosis. 19,38 Frontal dermoscopy will show hyperkeratosis and accumulation of white scales beneath the nail plate, which is more intensely attached to the nail plate in the toe nails than in the fingernails. 18,37 Subungual hyperkeratosis is silvery white but colour may change in case of infection.…”

Clinical value of dermoscopy in psoriasis

“…Nail psoriasis [26][27][28]33 Salmon patches Deep pitting Brownish band between the area of onycholysis and the normal nail Onychomycosis Spikes 27,56,57 : jagged edges with sharp whitish longitudinal indentations in the proximal portion of the onycholytic area Ruin pattern 27,58 : indentations on the ventral surface of the keratinocytes resulting in the accumulation of keratotic materials under the nail plate Longitudinal streak 27,56,59,60 : longitudinal streak on the nail plate, with changes in color ranging from bluish gray to black to whitish yellow Distal irregular termination 57,60,61 : the distal pulverization characteristic of the thickening of the nail plate in total dystrophic onychomycosis Traumatic onycholysis 27,28 The line of detachment of the nail plate from the nail bed is regular and smooth and is surrounded by a normal nail bed Allergic contact dermatitis due to artificial nails 62,63 Onycholysis with a dented border Periungual tissue damage Therefore, the utility of dermoscopy in the assessment of psoriasis severity needs to be demonstrated in further studies.…”