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Immunobullous disease
Immunobullous disease
In the setting of suspected immunobullous disease, biopsies for direct immunofluorescence should be taken from nonbullous lesional skin or perilesional skin within about 1 cm of a bulla. Nonbullous lesional skin has the higher yield.16 Lower extremity skin should be avoided because of a greater risk of false-negative results.17,18 Specimens for light microscopy should demonstrate an intact vesicle or bulla whenever possible. For larger lesions, the specimen should contain both portions of the blister and intact skin so that the edge of the blister and a portion of the bulla. A punch biopsy or shave excision works well for small vesicles, while a scooped shave may be useful to harvest larger bullae intact.
Tissue obtained for direct immunofluorescence should be placed in Michelโs medium or Zeus medium.19,20 Some immunodermatology laboratories prefer specimens transported in saline to reduce background staining. Saline-preserved specimens should be processed within 24 hours. If the specimen is inadvertently placed into formalin, it should immediately be removed and rinsed in normal saline. Brief formalin immersion produces false-negative results for pemphigus, but not for diseases characterized by deposits at the dermalโepidermal junction.21 In the setting of tense blisters suggesting a subepidermal bullous disease, a single punch technique has been used to obtain both H&E and DIF specimens and provide salt-split, skin like diagnostic information.22