Linear IgA Dermatosis – Bullous Disease of Childhood
Linear IgA disease (LAD) typically occurs after puberty with the majority of cases presenting after the age of 40. Chronic bullous disease of childhood (CBDC) usually presents before the age of 5. Both have a slight female predominance.
Patients with LAD present with pruritic, annular, or grouped papules, vesicles, or bullae distributed symmetrically on extensor surfaces. The clinical presentation may be indistinguishable from that of dermatitis herpetiformis. Patients may also present with lesions that appear similar to those found in bullous pemphigoid or epidermolysis bullosa acquisita. Oral and conjunctival surfaces may be involved resembling cicatricial pemphigoid. Rarely systemic symptoms such as fever, arthritis, arthralgias, and malaise may occur. This disorder has been associated with the intake of many drugs including vancomycin, lithium, and diclofenac. These patients also demonstrate a small increased risk of lymphoid malignancy.
In CBDC, young patients present with clustered, tense bullae, often on an inflammatory base giving a cluster of jewels appearance. Lesions are typically located in the perineum and perioral region. New lesions may appear around the periphery of previous lesions giving a giving the appearance of a collarette of blisters. The sensation of pruritus or burning is common.
For both disorders, blister formation is either within the lamina lucida or in the sublamina densa. On histopathologic exam, one finds subepidermal bullae with neutrophils along the basement membrane and at the papillary tips. Direct immuonfluorescence demonstrates linear IgA and indirect IF is typically positive for low titer circulating IgA antibodies. On salt-split skin, linear IgA deposits may be located in the lamina lucida similar to bullous pemphigoid, at and below the lamina densa similar to epidermolysis bullosa acquisita, or in both locations.
Both diseases are acquired autoimmune disorders that occur secondary to the formation of IgA antibodies that interact with a number of different antigenic targets. Circulating IgA antibodies that bind the epidermal side of salt-split skin typically bind to a 97 to 120 kDa antigen that is identical to a portion of the extracellur domain of BPAG 2 (180 kDa hemidesmosomal transmembrane antigen, also known as type XVII collagen). Circulating IgA antibodies that bind the dermal side of salt-split skin typically bind to the epidermolysis bullosa acquisita antigen, type VII collagen. There are also patients with a clinical presentation similar to cicatricial pemphigoid. These patients typically have IgA antibodies that bind to a 45 kDa antigen on the epidermal side of the basement membrane.
The course of LAD is unpredictable but most have disease that is present for years. Remission is unlikely. In contrast, CBDC is often a self-limited disease with remission occurring within two years of disease onset.