Epidermal transglutaminase ELISA test is the most sensitive serologic test for the diagnosis of dermatitis herpetiformis
Patients with dermatitis herpetiformis (DH) have always an associated gluten-sensitive enteropathy (GSE) that is frequently subclinical. The diagnosis of DH is based on the finding of granular deposits of IgA along the dermoepidermal junction and/or the dermal papillae by direct immunofluorescence, that can be found in all patients. However, these patients have circulating IgA antibodies directed against tissue transglutaminase (tTG), that correlate with the severity of GSE, and also indicate the adherence of this group of patients to a gluten-free diet. It has been recently shown that epidermal transglutaminase (eTG), an epidermal enzyme homologous to tTG, can be the autoantigen in patients with DH. In a recent study from Germany published in the July issue of the Journal of the American Academy of Dermatology the authors compared the levels of IgA autoantibodies against eTG and tTG tested by ELISA in a group of 52 patientswith DH. They found that when the patients were on a normal diet, 95% had autoantibodies against eTG, and 79% against tTG. In addition, they found that when the patients were on a gluten free diet and did not present any DH lesion, these autoantibodies were negative. The authors conclude that, in contrast to other previous studies, the eTG ELISA is currently the most sensitive serologic test for the diagnosis of DH.
Autoantibodies against epidermal transglutaminase are a sensitive diagnostic marker in patients with dermatitis herpetiformis on a normal or gluten-free diet
Rose C, Armbruster FP, Ruppert J, Igl BW, Zillikens D, and Shimanovich I.
J Am Acad Dermatol 2009;61:39-43.
Background. Dermatitis herpetiformis (DH) is a cutaneous manifestation of gluten-sensitive enteropathy (celiac disease). Patients with DH demonstrate circulating IgA antibodies against epidermal transglutaminase (eTG) and tissue transglutaminase (tTG). It has been suggested that eTG is the autoantigen of DH.
Objective. The purpose of this study was to characterize the autoimmune response to eTG and tTG in patients with DH on a normal or gluten-free diet (GFD).
Methods. Sera from 52 patients with DH were studied for the presence of IgA antibodies to eTG and tTG by enzyme-linked immunosorbant assay. In 38 patients, serum was obtained before initiation of a GFD, whereas 14 patients had been on a GFD for at least 2 years.
Results. Autoantibodies against eTG were detected in 36 of 38 patients (95%) and those against tTG in 30 of 38 patients (79%) with DH on a normal diet. Of 14 patients on a long-term GFD, 7 patients were free of DH lesions and did not require dapsone treatment. None of these patients showed circulating antibodies against eTG or tTG. The remaining 7 patients on a GFD were not able to stop taking dapsone. All these patients demonstrated anti-eTG antibodies, whereas only 3 of them showed additional reactivity against tTG.
Limitation. Autoantibody levels against eTG and tTG before and after introduction of a GFD were not examined in the same patients.
Conclusion. Our data suggest that antibodies to eTG are the most sensitive serologic marker in treated and untreated patients with DH and confirm the central role of eTG in the pathogenesis of this disease.
