dermatologic disorders
Bullous Pemphigoid
Diagnosis of Bullous Pemphigoid
Skin biopsy and IgG titers If blisters develop, bullous pemphigoid needs to be differentiated from Pemphigus Vulgaris , a blistering disorder with a worse prognosis; differentiation is usually possible using clinical criteria ( see Table: Test results help differentiate bullous pemphigoid from Pemphigus Vulgaris , If bullous pemphigoid is suspected, skin biopsy is done for histology and direct immunofluorescence testing. Samples from in and around the lesion itself are often used for histology, but samples of uninvolved skin (often about 3 mm from the edge of a lesion) are used for direct immunofluorescence. The blister in bullous pemphigoid is subepidermal, often containing many neutrophils and eosinophils. Direct immunofluorescence shows linear IgG and complement deposits along the basement membrane zone (dermal–epidermal junction). Indirect immunofluorescence shows circulating IgG deposits on the epidermal side of a salt-split preparation of normal (ie, test substrate) skin. Serum is tested for IgG antibodies to BPAg1 and BPAg2 using an enzyme-linked immunosorbent assay (ELISA). Circulating IgG autoantibodies are present in about three fourths of patients. 