Linear IgA disease

Linear IgA disease is also known as linear IgA bullous dermatosis; it is a rare, chronic, autoimmune pathology, affecting the skin and mucous membrane. It is subdivided into two types depending on the age of onset: adult and child bullous IgA dermatosis. As stated, this pathology is extremely rare and occurs mainly in China and some areas in southeast Asia; in Europe 1 case for every 250,000 people is reported. The variation affecting adults occurs mainly between 60 and 65 years of age with a slight preference for females. The most frequent variation in children occurs between 3 and 4 years of age.
The aetiology of bullous IgA dermatosis is unknown and it is, therefore, considered to have an idiopathic pathology. There also exists a drug-induced form, which mainly affects adults. From a histopathological point of view, bullous IgA dermatosis is characterised by linear deposits of IgA on the basal membrane. Antibodies target the proteins which are responsible for basal epithelial membrane adhesion (BP 180, protein hemidesmosomes and trans-membranous glycoproteins). The deposits of antibodies cause the activation of a complement and the attraction of neutrophils, thereby leading to a loss in adhesion and the formation of sub-epithelial blisters.
Clinically the pathology presents as vesicles and blisters widespread on the skin and ocular, oral and genital mucosa. The blisters are generally intact with a negative Nikolsky’s sign. The distribution of bullous IgA dermatosis in children typically resembles a string of beads whilst in adults the distribution is more heterogenous. There are cases whose occurrence is exclusively oral and not in the skin and vice versa. In the oral mucosa, the pathology predominates on the hard and soft palates and the buccal mucosa. Conjunctival, laryngo-pharyngeal and genital (vaginal or balanopreputial) lesions are also possible. In the skin, the trunk, the glans penis and the perineum are more involved. Ocular lesions in 50% of cases can result in scar which can cause a loss of sight.
A diagnosis of bullous IgA dermatosis can be made on a clinical basis, histological findings and direct immunofluorescence. Histologically, sub-epithelial blisters can be observed with a significant infiltration of neutrophils, eosinophils and lymphocytes. The most characteristic finding is obtained by direct immunofluorescence which highlights a linear deposit of IgA; this is negative for other immunoglobulins and fibrinogen. This result produces a diagnosis diagnosis from other vesicle-blister pathologies (such as: pemphigoid, dermatitis herpetiformis and epidermolysis bullosa). The treatment of choice is with Dapsone but haemolysis is a possibility in patients with a glucose-6-phosphate- dehydrogenase deficiency. In some cases Dapsone is used in conjunction with systemic corticosteroids.