|LETTERS TO THE EDITOR
|Year : 2019 | Volume
| Issue : 2 | Page : 187-189
Dermatoscopic features of prurigo nodularis
Pragya A Nair, Trusha Patel
Department of Dermatology and Venereology, Pramukshwami Medical College, Karamsad, Gujarat, India
|Date of Web Publication||15-Mar-2019|
Pragya A Nair
Department of Dermatology and Venereology, Pramukshwami Medical College, Karamsad - 388 325, Gujarat
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nair PA, Patel T. Dermatoscopic features of prurigo nodularis. Indian Dermatol Online J 2019;10:187-9
A 51-year-old male presented to dermatology services with complaints of itchy lesions on scalp, hands, trunk, and legs for the last 3 years. No history of trauma/prolonged standing and/or any comorbidities was reported. Family and personal history were not significant. Cutaneous examination revealed multiple well-defined discrete hyperpigmented papules, nodules, and plaques on forearm, dorsum of hands, and both legs [Figure 1]. Few papules and nodules were also present on face and scalp. Oral cavity and nail examinations were normal. Systemic examination was unremarkable. Routine baseline investigations were within the normal limits and serology was negative. Lesional skin biopsy was performed with possibilities of hypertrophic lichen planus (HLP), prurigo nodularis (PN), and chronic eczema,. Hand-held dermoscopy was performed with DE-300 (Firefly) polarizing digital dermatoscope with (20×) magnification, which showed red globules and peripheral striations [Figure 2]. Histopathology revealed hyperkeratosis, orthokeratosis, focal hypergranulosis, and irregular acanthosis with foci of pseudoepithelomatous hyperplasia. The papillary dermis showed inflammatory infiltrates, predominantly lymphocytes and few macrophages with vertically oriented collagen bands [Figure 3]. Focal spongiosis with lymphocytic exocytosis was noted, suggestive of PN. The patient was treated with potent topical steroids, emollients, and antihistamines.
|Figure 2: Hand-held dermoscopy with DE-300 (Firefly) polarizing digital dermatoscope with (×20) magnification showing red globules (black arrow) and peripheral striations (red arrow)|
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|Figure 3: Histopathology revealing hyperkeratosis, orthokeratosis, focal hypergranulosis, and irregular acanthosis with foci of pseudoepithelomatous hyperplasia. The papillary dermis showed inflammatory infiltrates of lymphocytes and few macrophages (hematoxylin and eosin stain 100×)|
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PN is a chronic inflammatory dermatosis of unknown etiology which commonly occurs between 20 and 60 years of age. Extensor surfaces of the lower extremities are the most common site. Trunk, upper extremities, and scalp can also be involved. Clinically, it is characterized by pruritic, 0.5–3 cm diameter, hyperpigmented or purpuric, firm nodules with a hyperkeratotic or excoriated surface.
PN needs to be clinically differentiated from dermatoses which may present with papulonodular lesions over extensor surface of lower limbs like HLP, nodular scabies, lichen simplex chronicus (LSC), lichen amyloidosis, multiple keratoacanthomas, and reactive perforating collagenosis. Histopathology supplemented by dermoscopy can be a useful diagnostic tool in differentiating PN from its differentials.
Dermoscopy is a recent diagnostic technique that enables clinicians to observe subsurface structures, and thus facilitates the clinical recognition of several inflammatory skin diseases and also reduces the need for biopsy.
The most common mimic of PN is HLP, which is characterized by extremely pruritic, and thick hyperkeratotic purplish or reddish plaques, on the shins or dorsal aspect of the foot. HLP and PN have clinical, histopathological, and dermoscopic similarities but both have some specific dermoscopic patterns that will help to differentiate them.
Dermoscopy of HLP and PN shows pearly white areas, more prominent and distributed over the entire periphery of the lesion in PN, but localized with few peripheral extensions in HLP. Peripheral extensions in PN give a “starburst” appearance, which correspond histopathologically to compact orthokeratosis above zones of wedge-shaped hypergranulosis and acanthosis; and peripheral striations which are more pronounced in PN corresponding to dermal fibrosis in histopathology.
The white starburst-like pattern (white lines arranged radially) on erythematous-brownish background is seen in nodular prurigo, while there is presence of whitish crossed lines (Wickham striae) in HLP.
Gray-blue globules on dermoscopy represent melanin pigment in the dermis caused by melanin incontinence and vacuolar degeneration. In HLP, diffuse structureless pattern interspersed in pearly white areas indicates presence of melanin incontinence in perifollicular and interfollicular areas, while they are not demonstrated in PN, suggesting absence of melanin incontinence.
Brownish-black dots which represent melanocytes and yellow structures which signifies vacuolar degeneration of the basal layer and spongiosis are not seen in PN. Comedone-like opening filled with yellow keratinous plugs referred to as corn pearls are observed in HLP but not in PN. Red dots which correspond to dilated capillaries in histopathology are observed in both HLP and PN. They are centrally located in PN in a “comma-like” pattern, whereas in HLP they are arranged diffusely in the lesions. Red globules which are larger than the red dots and correspond to enlarged blood vessels as well as focal hemorrhage in dermis, are more prominent in PN and are not seen in HLP.
Nodular scabies is a clinical variant of scabies that present with pruritic, erythematous nodules on the axillae, groin, and genitalia, rarely over extremities also. Dermoscopic findings show hang glider sign (the appearance of a brown triangle that corresponds to the head and the two anterior pairs of legs of the mite) or jet with condensation trails (the appearance of a brown triangle in addition to the white S-shaped burrows which are filled with eggs and scybala).
Keratoacanthoma (KA) is a common low-grade skin tumor, originating from neck of hair follicle. It is dome-shaped, symmetrical, surrounded by a smooth wall of inflamed skin, and capped with keratin scales and debris. It grows rapidly, reaching a large size within days or weeks, and then, necrose, slough, and heal with scarring. It is found on sun-exposed skin, often on face, forearms, and hands. A central brownish structureless area and hairpin vessels on a whitish background are the two main dermoscopic signs that favor a diagnosis of KA. Multiple KAs typically present as a central keratin crust surrounded by hairpin or linear irregular vessels with whitish halos.
LSC is a type of chronic eczema, where dermoscopy shows white structures, greyish-blue dots, and red dots. The white structures appears to correspond to hyperkeratosis while greyish-blue dots corresponded to dermal melanophages.
Lichen amyloidosis is a subtype of primary localized cutaneous amyloidosis. It presents as discrete, firm, closely set, dome-shaped brown papules commonly involving the anterior aspect of shins and extensor surfaces of forearms.
The most common dermoscopic finding of both macular amyloidosis and lichen amyloidoses 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. In addition, in lichen amyloidoses 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).
Acquired perforating dermatosis constitutes a group of dermatoses that are characterized by transepithelial elimination of altered dermal material (collagen, elastic fibers, and/or hair follicle). It occurs in adulthood and is commonly associated with diabetes mellitus and chronic kidney disease, also with liver failure, hypothyroidism, hyperparathyroidism, pulmonary fibrosis, HIV/AIDS, scabies and neoplasias. Clinically, they are characterized by papules or crateriform nodules with a central keratotic plug which may have follicular pattern mainly affecting the extensor surface of the limbs and the trunk.
Dermoscopy of reactive perforating collagenosis shows central white area, yellow plugs of keratin with variable size (possibly corresponding to the area of fibrosis and extrusion of dermal material), a keratotic collarette with a brown-grayish amorphous, or erythematous area surrounding it, possibly due to inflammatory reaction as dotted vessels.
Thus, specific dermatoscopic patterns may help in differentiating nodular lesions over extensor aspects of lower limbs.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]