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Therapeutics in Dermatology
A reference textbook in dermatology
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Linear IgA bullous dermatosis

17 April 2012, by INGEN-HOUSZ-ORO S. , DOEBELIN B. & CLAUDY A.

1 - BACKGROUND

Linear IgA bullous dermatosis (LIgAD) is an auto-immune subepidermal bullous disorder characterised by linear IgA deposits at the dermal-epidermal junction. It is caused by autoantibodies directed against a molecule in the dermo-epidermal basement membrane, a proteolytic fragment of BP180, with a molecular mass of 97 or 120 kD. It is a rare disorder (less than 1 case/106/year) but it is the most common auto-immune bullous dermatosis in children arising in the first decade of life. It may be either idiopathic or triggered by a variety of medications after an induction period of a few days to a few weeks [1]. It arises most often with vancomycin [2], but has been reported with other molecules, including anti-epileptics [3], antibiotics, non-steroidal anti-inflammatories [4] and ACE inhibitors, etc. [5].

 The clinical presentation in children is often highly typical, with clusters of tense bullae of varying sizes arising predominantly on the genitals, face and ears. The bullae are sometimes, but not always, itchy. In adults, the clinical picture is more variable, ranging from the symptoms and signs of dermatitis herpetiformis, with vesicular bullous lesions on the buttocks and extensor surfaces of the limbs to bullous pemphigoid with bullae containing clear or bloody fluid on erythematous or urticarial skin and mucosal pemphigoid, with possible involvement of the whole mucosa and a risk of ocular senechia [6]. Other clinical pictures are also possible, including a non bullous form [7] and a pseudo-toxic epidermal necrolysis form [8].

Histologically, the disorder presents as sub-epidermal bullae with an inflammatory dermal infiltrate consisting of neutrophils and eosinophils. These may cluster to form micro-abscesses crowning the dermal papillaries and closely resembling dermatitis herpetiformis. Direct immunofluorescent examination of the skin surrounding the bullae shows linear IgA deposits, sometimes combined with complement fraction C3. Indirect immunofluorescence occasionally shows low titre IgA autoantibodies. Indirect immunofluorescence in M NaCl split skin is more sensitive, with staining in the epidermal and/or dermal layers. Electronic immunomicroscopy studies show that the deposits are located in the lamina lucida and/or the lamina densa ("mirror" image which is more suggestive of LIgAD).

An immunotransfer study highlights the distinctive 97/120 kD fragment, sometimes combined with other antibodies such as BP230, BP180 and collagen VII.

From a pathophysiological standpoint, the disorder is caused by IgA immune complexes which generate an inflammation cascade with complement activation and involvement of proinflammatory cytokins and proteases.

Drug-induced LIgAD is generally self-limiting a few days or weeks after the responsible drug has been withdrawn. Conversely, LIgAD is a chronic condition with an often unpredictable course punctuated by relapses for which treatment must be pursued at the minimal effective dose until negative direct immunofluorescence results are obtained. 

Some mucosal forms of LIgAD may have severe functional complications such as cicatricial pemphigoid. The main mucosal forms of LIgAD are therefore considered to belong to the mucosal pemphigoid disease spectrum.

Blood disorders and cancers (Hodgkin’s disease and cancers of the bladder, oesophagus, breast, kidney and colon) have been described in conjunction with LIgAD, but the number of cases reported is not sufficient to exclude the possibility of a chance combination [10, 11].

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