Data from our series of 70 patients support the hypothesis that linear IgA disease is a heterogeneous disease as regards clinical features, target antigens and immunogenetics. The clinical presentation varies as regards age of onset and severity of skin and mucosal involvement and scarring. The use of split skin and of the novel substrate cylindroma has identified 2 target antigens. The majority of patients have a target antigen associated with epidermal cells and possibly cylindroma hemidesmosomes. A minority have a dermal antigen which resembles collagen VII on cylindroma. There is an association with HLA-B8, -DR3, -Cw7 and with the linked rare tumour necrosis factor a allele, but this is not universal. These differences do not correlate with each other.