| Summary: | Background: When performing direct and indirect skin immunofluorescence (DIF, IIF) in bullous pemphigoid (BP) utilizing single fluorophores such as fluorescein isothiocyanate (FITC), the presence of ”background” fluorescence is commonly described. Aim of reporting this case: Our laboratory has noted that what is termed “background” could represent a complex immune response in BP, that may be present in addition to the classical deposits of immunoglobulins and/or complement at the dermal/epidermal basement membrane zone (BMZ). Therefore, we simultaneously used multiple colored fluorophores to further investigate this possibility. Case Report: A 68-year-old male was evaluated for the presence of rapidly appearing vesicles and bullae on the chest, with additional pruritus. Methods: Skin biopsies for hematoxylin and eosin (H&E) staining, as well as for DIF, IIF, salt split skin and immunohistochemistry (IHC) analyses were performed. Results: H&E staining demonstrated a subepidermal blistering disorder. Within the dermis, a mild, superficial and deep, perivascular infiltrate of lymphocytes, histiocytes and eosinophils was observed. A few infiltrate cells displayed positive DIF staining for CD5, CD8 and CD45 around dermal blood vessels, nerves and eccrine sweat glands. In contradistinction, CD4, CD56 and Granzyme B staining was predominantly negative in these areas. DIF, IIF and salt split skin studies revealed a strong presence of IgG, Complement/C3, IgM and fibrinogen in linear patterns at the BMZ. Around the upper dermal perivascular infiltrate, HAM56 and CD68 positive cells were also noted. Positive DIF staining for CD1a was found suprajacent to the blister in the epidermis. Utilizing identical antibodies, we repeated our staining with the IHC technique, to address the issue of autofluorescence in DIF staining. Our IHC findings correlated with DIF and IIF results. Conclusion: Using multiple DIF fluorophores in this case of BP, we observed autoantibodies to structures such dermal nerves, blood vessels and eccrine sweat glands, that were not appreciated using FITCI alone. We propose the use of this technique in autoimmune skin diseases. In addition, we observed a prominent T cytotoxic cell infiltrate, that warrants further characterization.
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