Induction of lesions of dermatitis herpetiformis by autologous serum

In the present study various factors which contribute to the initiation of lesions in dermatitis herpetiformis (DH) were examined. Thirty-one patients with DH, seven with bullous pemphigoid, two with linear IgA disease and two healthy subjects were studied either before starting treatment or after stopping dapsone for up to 5 days. Intradermal inoculation of freshly prepared autologous serum was followed after 18-24 h by the formation of DH-like lesions in 24/31 DH patients. The lesions were erythematous papules, often with vesicles and microscopically showed papillary tip microabscesses. Serum-induced formation of lesions only occurred in patients with active DH with some spontaneous lesion formation: it did not occur in any of the non-DH controls. The formation of lesions was dose-related, declining proportionately with dilution of the serum down to 1/16. Plasma prepared by various methods of anticoagulation (heparin, citrate, EDTA) caused lesser reactions, while addition of heparin or epsilon-amino caproic acid (EACA), but not citrate, to serum substantially inhibited the formation of lesions. This suggested the responsible factor might be a protease. Other vasoactive agents including histamine (1-4 micrograms) and compound 48/80 (1-5 micrograms) caused normal immediate wealing. DH-like lesions occurred in only one of 13 subjects challenged with histamine and two of nine challenged with 48/80. In all these, autologous serum elicited large vesicular responses. There is a factor(s) in serum in DH which can initiate the formation of lesions. This factor appears to be activated by clotting and can be inhibited by heparin and EACA, suggesting it may be a protease.