S11C22bP17b-Scabies

S11C22bP17b-1: The epidermis is hyperplastic in psoriasiform patterns. In addition, the epidermis shows spongiosis and spongiotic vesicles. Perivenular infiltrates extend along vessels from the region of the interface between the papillary dermis and the reticular dermis to the lower margin of the dermis. They extend into the subcutaneous fat. In the upper portion of the dermis, there are interstitial infiltrates of lymphoid cells among collagen bundles of the reticular dermis. The infiltrates extend into the epidermis in areas of spongiosis. The patterns are both spongiotic and psoriasiform. Features of a lymphocytic vasculitis also are represented. This is a common pattern of an “insect bite” reaction (scabies).

S11C22bP17b-2: A reaction to an “insect bite” (an arthropod reaction) has vasculitic qualities in the reticular dermis. In addition, a lymphohistiocytic collagenosis usually is associated with an eosinophilia, as is seen in this field. The inflammation is associated with activation of connective cells. Focally, vessels, in this type of reaction, may show fibrinoid necrosis.

S11C22bP17b-3: The interstitial infiltrates consist of lymphocytes, histiocytes, eosinophils, and activated connective tissue cells. In this type of reaction, plasma cells often are a component of the perivascular infiltrates. The lymphoid infiltrates may contain transformed (large) cells. There are fragments of nuclear debris (blue arrows).

S11C22bP17b-4:A portion of an ectoparasite is represented in a “tunnel” in the keratin layer. This probably is a portion of the shell of an empty egg. The spongiotic vesicle at the bottom of the field is rich in histiocytes and eosinophils (eosinophilic spongiosis ).

S11C22bP17b-5: With a PAS stain, a mature parasite is represented in a “tunnel” in the keratin layer. To the left, faintly yellow spines are represented.

 

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