Diagnosis: Direct Immunofluorescence
• Direct immunofluorescence detects antibodies located in a skin biopsy specimen of an affected patient and is a useful tool in the diagnosis of autoimmune blistering and inflammatory disorders. The highest diagnostic yield direct immunofluorescence comes from biopsy specimens of perilesional skin adjacent to a blister. Skin from the lower extremity should be avoided because it may be prone to false-negative reactions.
• Subepidermal blistering disorders that show a linear pattern of staining at the dermal-epidermal junction include bullous pemphigoid (IgG and C3), pemphigoid gestationis (C3), epidermolysis bullosa acquisita (IgG), and linear IgA disease (IgA). A granular pattern at the dermal-epidermal junction is seen in dermatitis herpetiformis (IgA) and in lesional skin of lupus erythematosus (IgG, IgM, IgA, and C3).
• Direct immunofluorescence on salt-split skin is helpful in differentiating bullous pemphigoid from epidermolysis bullosa acquisita, which both show linear IgG staining at the basement membrane zone. On salt split skin, bullous pemphigoid shows staining on the epidermal side of the blister, whereas epidermolysis bullosa acquisita shows staining on the dermal side of the blister.
• Pemphigus vulgaris and pemphigus foliaceus are both characterized by deposition of immunoglobulins between the cells of the epidermis on direct immunofluorescence. The staining is more prominent in the superficial epidermis in pemphigus foliaceus.
• Acantholytic disorders that may mimic pemphigus vulgaris on histologic examination but for which direct immunofluorescence is negative include Hailey-Hailey disease, Grover disease, and Darier disease.
