S7C5P2-Linear igA Dermatitis

S7C5P2-1: The pattern is that of a ruptured, sub-epidermal vesicle. The vesicle is cell-poor at the dermal-epidermal interface (dermal side). An infiltrate of inflammatory cells (mostly neutrophils) has collected along the floor of the defect. The roof of the vesicle shows a basal unit that is fairly uniformly represented; a basal layer focally is recognizable. In the roof, the superficial unit is thin. The defect contains extravasated red blood cells. To the right of the field, beyond the main defect, neutrophils have collected at the dermal-epidermal interface; they are associated with lytic clefts. The papillary dermis and the upper portion of the reticular dermis are edematous (linear IgA dermatitis).

S7C5P2-2: In this area, the infiltrates of neutrophils and histiocytes are arranged in a linear pattern along the dermal-epidermal interface. Some of the basal keratinocytes (blue arrows) show cytopathic changes with pyknosis of nuclei and condensation of cytoplasm (increased cytoplasmic acidophilia). In the spotty defects at the dermal-epidermal interface, migratory histiocytes are admixed with the neutrophils. The papillary dermis, in the region of the infiltrates, is edematous.

S7C5P2-3:  Mild cytopathic changes are evident at the dermal-epidermal interface (green arrows). Some of the keratinocytes show condensed, acidophilic cytoplasm, particularly on the basement membrane side of the nucleus. Inflammatory cells at the dermal-epidermal interface, including neutrophils and histiocytes, show degenerative changes (cytolytic changes with some degree of karyolysis); these changes in inflammatory cells are associated with the release of digestive enzymes into the tissue. A red arrow identifies a better preserved neutrophil.

S7C5P2-4: In this field, the interface changes have dissected along a hair follicle (linear IgA dermatitis).

S7C5P2-5: On the left, the epidermis is hyperplastic; the character of the keratin layer might offer support for the interpretation that the biopsy site is acral. The papillary dermis is widened and fibrotic. There are spotty perivascular infiltrates of inflammatory cells. Focally, the infiltrates fill a widened dermal papilla; they press upon the epidermis. On the right (at a higher magnification), the dermal papilla has separated from the epidermis and, in the defect between the epidermis and the dermal papilla, an infiltrate of neutrophils has collected. This is a well-developed supra-papillary abscess of dermatitis herpetiformis.

S7C5P2-6: Immunofluorescent patterns of the lesion of DH seen in S7C5P2-5 are represented. In the IgA field (bottom on left), this broken pattern might be mistaken for the linear deposits of linear IgA dermatosis.

S7C5P2-7: This example of linear IgA bullous dermatosis is characterized by a ruptured bulla on the right at the margin of the biopsy. The defect contains condensed fibrin. To the left of the bulla, the epidermis has separated from the dermis to produce a linear defect with a suggestion of festooning along the floor of the defect.

S7C5P2-8: In this field, there is a suggestion of preservation of papillae along the floor of the defect. There is a suggestion of an accentuation in the cellular density of the infiltrates in dermal papillae and at the tips of the papillae. The patterns are not sufficiently defined to be cited as evidence favoring either dermatitis herpetiformis, or linear IgA bullous dermatosis.

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