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HYDROA AESTIVALE
Hydroa aestivale is a light-sensitive, vesicular eruption. It is a cytolytic disorder in which the vesicular
changes are spongiotic and reticulated. The basal unit is hyperplastic; cells of the basal unit undergo cytolysis and coagulative necrosis.
Plate-like areas of necrosis of the superficial unit of the epidermis may be a feature. Vacuolar changes at the dermal-epidermal interface are associated with infiltrates of lymphocytes, histiocytes, and neutrophils in interface patterns (S7C12P9-1-3). Edema of the papillary dermis may be a feature.
The nature of the disorder is uncertain; some cases may be related to erythropoietic protoporphyria. In a recent
case, which clinically was thought to be hydroa, the lesion was micro-pustular; infiltrates of neutrophils and histiocytes were present in the adjacent epidermis (S7C12P9-4 & 5).
In areas, the adjacent epidermis showed cytolytic changes; the patterns were “moth-eatened.” The epidermal defects were manifested in reticulated patterns (S7C13P10-3-6). The dermis contained perivascular infiltrates of lymphocytes, histiocytes and neutrophils. Similar infiltrates were present
interstitially among collagen bundles of the reticular dermis (S7C13P10-1 & 2). In this case, immunoreactions for herpes simplex virus
antigen, type I & II, were positive in the nuclei of the keratinocytes in the region of the vesicles.
STAPHYLOCOCCAL SCALDED SKIN SYNDROME
A well-developed lesion of pemphigus foliaceus generally presents a fairly characteristic histologic pattern.
Occasional cases, purported to be staphylococcal scalded skin syndrome (SSSS), show epidermal changes strongly suggestive of pemphigus foliaceus (S7C14P11-1-4).
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