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. 2021 Jan 1;184(1):141–150. doi: 10.1111/bjd.19415

Figure 2.

Figure 2

Comparative light microscopic findings and myxovirus resistance protein A (MXA) pattern of immunoreactivity in COVID‐19‐associated perniosis, idiopathic perniosis and COVID‐19‐associated thrombotic retiform purpura. (a) In acral perniosis of mild COVID‐19, a striking inflammatory response is observed characterized by a mononuclear‐cell‐dominant interface dermatitis with an associated intense superficial and deep angiocentric lymphocytic and histiocytic infiltrate that surrounds and infiltrates the vessel walls of capillaries, venules and arterioles and is found in close apposition to the eccrine ducts and glands of the eccrine coil [haematoxylin and eosin (HE), original magnification × 40]. (b) In contrast, with the livedoid rash of severe COVID‐19 there is a pauci‐inflammatory thrombogenic vasculopathy that in this case involves the arterial system (HE, × 40). (c) In COVID‐19‐associated perniosis there is immunoreactivity for MXA within the epidermis and endothelial cells and amid inflammatory cells [diaminobenzidine (DAB), × 40]. (d) A virtually identical pattern of immunoreactivity is observed for MXA in idiopathic perniosis (DAB, × 40). (e) In the paucicellular thrombotic retiform purpura of severe COVID‐19 there is no immunoreactivity for MXA (DAB, × 40). NK, natural killer; TH, T helper cell. Scale bars are set at 650 microns.