OTHER BULLOUS ERUPTIONS THAT MAY BE CONFUSED WITH AUTOIMMUNE BLISTERING DISEASES
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membrane zone First-line therapy is dapsone Other therapies include prednisone, sulfapyridine, colchicine, erythromycin, and topical steroids The condition tends to spontaneously remit over months to years but occasionally can be chronic Bullous Pemphigoid Bullous pemphigoid is a rare autoimmune blistering disorder that may develop as early as the newborn period and is due to autoantibodies to one of two hemidesmosomal proteins, BP 230 and BP 180, which help to maintain dermal– epidermal attachment Primary lesions include diffuse, large, tense, clear, or hemorrhagic bulla on a noninflammatory or erythematous base, although urticarial lesions occasionally predominate Common locations include forearms, abdomen, thighs, genitals, palms, and soles The striking acral involvement is more common in infancy and may help to distinguish clinically from other autoimmune blistering diseases Mucosal involvement may be seen Pruritus is common and may be severe Diagnosis is confirmed by biopsy of a vesicle demonstrating a subepidermal bulla with a predominantly eosinophilic infiltrate, and DIF from perilesional skin revealing linear deposition of immunoglobulin G (IgG) and C3 Enzyme-linked immunosorbent assay (ELISA) of BP 230 and 180 is commercially available as is indirect immunofluorescence testing for autoantibodies in the blood BP may also be initially confused with bullous impetigo The mainstay of treatment is oral corticosteroids, and the disease lasts an average of year Dermatitis Herpetiformis DH presents as symmetric, intensely pruritic, crusted papules, papulovesicles, and urticarial plaques overlying extensor surfaces of the elbows and knees, posterior neck, scalp, and buttocks Children with DH have gluten-sensitive enteropathy, however many are asymptomatic Only about 10% of patients with a diagnosis of celiac disease will present with the classic eruption of DH TABLE 67.3 AUTOIMMUNE BULLOUS DISORDERS OF CHILDHOOD Chronic bullous disease of childhood Type of lesions Distribution Bullous pemphigoid Large, tense, clear Large, tense Grouped bullae; annular bullae papulovesicles, plaques with bullae, or active vesicular urticarial borders lesions Scalp, lower Trunk and flexor Back, buttocks, trunk, genitals, surfaces of scalp, extensor buttocks, inner extremities surface of thighs extremities, often symmetric None to severe Mild Intense Occasionally Yes No Pruritus Mucous membrane involvement Duration Months to years Months to years Immunofluorescence + or − + Linear IgA Linear IgG on basement basement membrane (+ membrane (+ circulating IgA) circulating IgG) Treatment Dermatitis herpetiformis Dapsone > Corticosteroids Corticosteroids Months to years + Granular IgA at tips of dermal papilla of uninvolved perilesional skin Dapsone > Sulfapyridine Diagnosis is confirmed by biopsy of a papule or vesicle showing a predominately neutrophilic infiltrate focused at the tip of the dermal papillae DIF reveals granular IgA deposition at the dermal papillae Diagnosis may also be made by circulating serum IgA antibody to tissue transglutaminase in the blood IgA levels should be checked as IgA deficiency may lead to a false-negative test Additional diagnostic tests often included in a celiac panel include antiendomysial antibodies and antigliadin antibodies Patients with DH should undergo endoscopy to assess for clinical evidence of gluten-sensitive enteropathy Treatment includes dapsone, which leads to spontaneous remission of DH in 24 to 48 hours Strict adherence to a gluten-free diet is recommended and may obviate the need for dapsone For comparison of the above autoimmune bullous diseases, see Table 67.3 Systemic Lupus Erythematosus Although not characteristic, widespread tense, bullous lesions can occur in systemic lupus erythematosus (SLE), usually in sun-exposed areas Multisystem involvement suggests the diagnosis Laboratory confirmation, which may include a skin biopsy and lupus band test, in conjunction with the complete clinical picture, is necessary for diagnosis OTHER BULLOUS ERUPTIONS THAT MAY BE CONFUSED WITH AUTOIMMUNE BLISTERING DISEASES Many times, the appearance of a rash is so characteristic that a diagnosis becomes obvious Such is the case with the conditions listed below, which are discussed in more detail in their respective chapters but are mentioned here for completeness when considering a vesiculobullous eruption Linear or geometric areas of vesiculation are the best clues to the presence of allergic contact dermatitis (see Chapter 65 Rash: Atopic/Contact Dermatitis and Photosensitivity ) The shape of the dermatitis provides the information that helps identify the offending agent A history of playing in a shrubbed area, camping, hiking, or being near burning leaves is helpful Because children brush against poison ivy leaves, vesicles often are in a line and on exposed surfaces (e.g., the face, extremities) A round group of vesicles on the back of the wrist would point to contact sensitivity to nickel contained in the metal case of a wristwatch Dermatomal distribution of vesicles or bullae usually indicates the presence of herpes zoster On rare occasions, in infants, the same dermatomal appearance may represent zosteriform herpes simplex infections Viral cultures, rapid slide tests using monoclonal antibodies, or more recently, polymerase chain reaction tests are utilized to differentiate herpes simplex from herpes zoster Target or iris lesions are pathognomonic of erythema multiforme The lesion has a dusky center that may blister and has successive bright red bordering rings At times, a doughnut-shaped blister occurs ( Fig 67.7 ) This contrasts with annular urticaria, in which incompletely round (arcuate or polycyclic) wheals are observed and individual lesions typically resolve within less than 24 hours (see Chapter 68 Rash: Drug Eruptions ) CBDC may be confused with erythema multiforme as discussed above FIGURE 67.7 Erythema multiforme on the hand with large, target-shaped lesions with central blistering due to recurrent herpes simplex labialis