Linear IgA bullous disease
This is clinically similar to pemphigoid, but affects children as well as adults. Blisters arise on urticarial plaques, and are more often grouped, and on extensor surfaces, than is the case with pemphigoid. The so-called ‘string of pearls sign’, seen in some affected children, is the presence of blistering around the rim of polycyclic urticarial lesions. The conjunctivae may be involved. Linear IgA bullous disease is, as its name implies, associated with linear deposits of IgA and C3 at the basement membrane zone (Fig. 9.5). IgG is sometimes also found. The disorder responds well to oral dapsone.