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. 2021 Jul 22;39(6):934–965. doi: 10.1016/j.clindermatol.2021.07.001

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Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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Fig 4 — Thrombotic retiform purpura (SARS-CoV-2 viral capsid, cytokine, and furin immunohistochemical assessment). In each of thrombotic retiform purpura cases, localization of the SARS-CoV-2 capsid protein within the endothelium, including spike glycoprotein, capsid membrane, and capsid envelope, is observed but not intact virus. (A), (B) Spike glycoprotein endothelial cell localization within the deep dermal and subcutaneous microvessels in a patient who succumbed to COVID-19 (A, red chromogen, 1000 ×; B, red chromogen, 400 ×). At autopsy, the patient had classic thrombotic retiform purpura, which was biopsied. (C) In this case and other similar cases, the viral capsid protein localization is most apparent in the deeper dermal and subcutaneous microvessels and mirrors the distribution of ACE2 expression in microvessels of the skin and subcutaneous fat (DAB, 1000 ×). (D) The deep dermal and subcutaneous vessels that expressed spike glycoprotein (DAB, 1000 ×) also show (E) IL-6 (red chromogen, 1000 ×) and (G) TNF α expression (red chromogen, 1000 ×) whereby (E) endothelial cell colocalization of spike glycoprotein and IL-6 and spike glycoprotein and TNF α can be demonstrated using a nuance software that converts the red chromogen stain into a red signal (red chromogen, 1000 ×) and (D) the DAB stain into a green signal. (F), (H) Areas of colocalization appear yellow. In another case of thrombotic retiform purpura, there was very striking expression of furin within (I) endothelium in contrast with (J) its minimal expression in endothelium of biopsied normal deltoid skin in a healthy adult woman. ACE, angiotensin-converting enzyme; COVID-19, coronavirus disease 2019; DAB, diaminobenzidine; IL, interleukin; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TNF, tumor necrosis factor.

Fig 4 — Thrombotic retiform purpura (SARS-CoV-2 viral capsid, cytokine, and furin immunohistochemical assessment). In each of thrombotic retiform purpura cases, localization of the SARS-CoV-2 capsid protein within the endothelium, including spike glycoprotein, capsid membrane, and capsid envelope, is observed but not intact virus. (A), (B) Spike glycoprotein endothelial cell localization within the deep dermal and subcutaneous microvessels in a patient who succumbed to COVID-19 (A, red chromogen, 1000 ×; B, red chromogen, 400 ×). At autopsy, the patient had classic thrombotic retiform purpura, which was biopsied. (C) In this case and other similar cases, the viral capsid protein localization is most apparent in the deeper dermal and subcutaneous microvessels and mirrors the distribution of ACE2 expression in microvessels of the skin and subcutaneous fat (DAB, 1000 ×). (D) The deep dermal and subcutaneous vessels that expressed spike glycoprotein (DAB, 1000 ×) also show (E) IL-6 (red chromogen, 1000 ×) and (G) TNF α expression (red chromogen, 1000 ×) whereby (E) endothelial cell colocalization of spike glycoprotein and IL-6 and spike glycoprotein and TNF α can be demonstrated using a nuance software that converts the red chromogen stain into a red signal (red chromogen, 1000 ×) and (D) the DAB stain into a green signal. (F), (H) Areas of colocalization appear yellow. In another case of thrombotic retiform purpura, there was very striking expression of furin within (I) endothelium in contrast with (J) its minimal expression in endothelium of biopsied normal deltoid skin in a healthy adult woman. ACE, angiotensin-converting enzyme; COVID-19, coronavirus disease 2019; DAB, diaminobenzidine; IL, interleukin; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TNF, tumor necrosis factor.