Diagnostic Immunopathology in 21 Century Dermatology Part I: Basics and Epidermal Deposits

Immunofluorescence techniques and other immunopathologic diagnostic techniques in dermatology involve the detection and localization of specific autoantibodies against various antigens within the skin. Since the 1960s when the lupus band test was utilized to diagnose lupus erythematosus, diagnostic immunopathologic techniques, when interpreted alongside clinical and histopathologic findings, have become a part of the diagnostic criteria in the diagnosis of many skin diseases, in particular the autoimmune blistering diseases and connective tissue diseases. This article gives an overview of basic and updated immunopathologic techniques used in the diagnosis of many dermatologic conditions, based on the pattern of immunofluorescence staining: epidermal intercellular staining encompasses the pemphigus group and its variants, while keratinocyte cell surface staining with dermoepidermal junction staining leads to the diagnosis of paraneoplastic pemphigus. Staining of the basement membrane zone points to the diagnosis of the subepidermal blistering diseases, including the pemphigoid group and variants, epidermolysis bullosa acquisita, linear IgA bullous dermatosis or dermatitis herpetiformis. Shaggy fibrinogen staining at the basement membrane zone with cytoid bodies is characteristic of lichen planus. Vascular staining may help diagnose immune complex vasculitis, and homogeneous vascular staining combined with dermoepidermal staining suggests the diagnosis of porphyria cutanea tarda. The significance of other patterns of staining like cytoid bodies (found in interface dermatitis like lichen planus and lupus erythematosus), and anti-nuclear fluorescence (seen in mixed connective tissue disease) are also discussed. Clinical features, common immunofluorescence findings and adjunctive immunopathologic techniques like immunoblotting are detailed. The advancement of current knowledge at the molecular level is rapid, leading to the precise identification of target antigens, and production of recombinant proteins used in enzyme-linked immunosorbent assays (ELISA), which are highly sensitive and specific tests that calls into question the relevance of more traditional immunofluorescence techniques. (Dermatol Sinica 26: 119137, 2008)