Dermoscopy of a Case of Pseudoxanthoma Elasticum: A Step Closer to Diagnosis.

Sir,

A 20-year-old female with Fitzpatrick skin type V presented with complaints of asymptomatic yellowish papules over both sides of neck, gradually progressing to form plaques for the past 7 years. Family history of similar lesions was absent. There were no associated systemic complaints. On examination, multiple, monomorphic, yellowish papules coalescing to form plaques with cobblestone appearance over lateral aspect of neck bilaterally were present [Figure 1a and b]. Dermoscopic examination of the plaques (DermLite II hybrid m; 3Gen; noncontact polarized mode, 10x magnification, images captured using DermLite adapter for iPhone X) revealed multiple, yellowish-white structures coalescing irregularly to form linear streaks, interspersed with areas of ill-defined faint erythema [Figure 2a and b]. Exaggerated pigment network was also appreciated. Fundus examination, echocardiography, routine urine, and stool examination were done and were within normal limits. Upon histopathological examination, multiple, irregular, short, and frayed basophilic elastin fibers were appreciated in the mid dermis, giving it a raveled wool appearance. Apart from the presence of dilated vessels, papillary dermis was uninvolved [Figure 3a-c]. von Kossa stain confirmed the presence of calcium deposits [Figure 3d]. A final diagnosis of pseudoxanthoma elasticum (PXE) was made after clinic-pathological correlation. Upon dermoscopy, background erythema along with either absent or when present, subtle vessels seen in PXE help differentiate it from PXE-like PDE, which shows yellowish clods over a flesh-colored background and marked linear vessels.

Figure 1

(a, b) Multiple, yellowish papules coalescing to form plaques over both sides of the neck

Figure 2

(a) Dermoscopy under polarized light (DermLite II Hybrid M, 3Gen, San Juan Capistrano, CA, USA; 10× magnification) of plaque over neck showing multiple, yellowish-white structures (black arrow) coalescing irregularly to form linear streaks, interspersed with areas of ill-defined faint erythema (b) closer view to visualize irregular yellowish-white structures (black arrow) intermingled with faint erythema and exaggerated pigment network

Figure 3

(a) Unremarkable epidermis with irregular and frayed elastic fibers in mid-dermis. Papillary dermis is spared apart from dilation of vessels (H and E, 4×); (b) multiple, short, curled basophilic elastic fibers seen (H and E, 10×); (c) Higher power showing fragmented, granular elastic fibers giving a raveled wool appearance (H and E, 40×); (d) von Kossa stain shows presence of calcium deposits. Inset shows closer view of calcium deposits (von Kossa, 40×)

PXE is a rare, inherited, elastolytic disorder, caused by mutations in the ABCC6 (ATP-binding cassette) gene primarily affecting skin, eyes, and cardiovascular system.[1] Skin manifestations include yellowish papules over flexural areas which coalesce to form leathery plaques. Dermoscopic findings of irregular yellowish-white structures seen in the present case are in-line with the previous reports.[1234] The yellowish-white structures are believed to represent mid-dermal degeneration of elastic fibers or calcium deposits.[1] The ill-defined areas of faint erythema seen on dermoscopy in the present case could be secondary to vasodilation caused by underlying elastolysis. Dermoscopic findings of PXE previously reported are summarized in Table 1. An important differential to be considered when a patient presents with skin-colored papules over photo-exposed areas is PXE-like papillary dermal elastolysis (PXE-like PDE), which is a rare disorder with cutaneous findings similar to PXE.[5] Unlike PXE, lesions of PXE-like PDE do not show calcification of distorted elastic fibers with von Kossa stain.[5] Dermoscopy of PXE-like PDE has been reported to show light-yellow clods over a flesh colored background and marked linear vessels.[1] Presence of background erythema along with either absent or when present, subtle vessels on dermoscopy help differentiate PXE from PXE-like PDE, where the yellowish clods are present over a flesh colored background along with marked linear vessels.[AQ: This sentence “Presence of background erythema…” lacks in clarity. Please rephrase it as required.]

Table 1

Summary of dermoscopic findings of PXE

Study [citation], Year of publication	No. of cases reported	Dermoscopic features
Lacarrubba et al.[2] 2017	2	Multiple irregular yellowish areas coalescing to form linear, parallel strands in one case.
		Multiple blotchy, yellowish areas alternating with prominent superficial linear vessels in the second case.
Singh et al.[3] 2017	1	Multiple irregular yellowish areas arranged as linear strands alternating with multiple linear vessels.
Kawashima et al.[1] 2018	2	Coalescing and reticulated yellowish-white clods on a light purplish-red background and subtle reticulated vessels in one case.
		Yellowish-white clods on a light purplish-red background with a lack of vessel findings in the second case.
Salas-Alanis et al.[4] 2019	1	Multiple irregular yellowish-white areas alternating with prominent superficial linear vessels, on a light purplish-red background.

PXE is associated with considerable morbidity owing to ocular involvement which can lead to blindness and cardiovascular complications which range from intermittent claudication to occasional myocardial infarcts and rupture of blood vessels in gastrointestinal tract rarely.[4] This makes prompt diagnosis of this disorder imperative to workup the patient for systemic involvement, if any, early.

In conclusion, dermoscopy can act as a useful, noninvasive modality for early diagnosis of this rare, multisystem disorder, helping in the differentiation of PXE from its close clinical mimickers.

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Conflicts of interest

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