M2033 Role of Antibodies in the Long Term Follow Up of Patients with Celiac Disease to Predict the Adherence to Gluten-Free Diet

Abstract

Introduction: The prevalence of celiac disease (CD) is 0.5-1% in the Western population. As CD is widely underdiagnosed, the majority of CD patients is still untreated and therefore at greater risk of developing complicated CD, including Enteropathy Associated T-cell Lymphoma (EATL). Differentiation between various T-cell lymphomas is difficult because of similar morphology and immunophenotype. The final diagnosis is based on clinical presentation and localisation of the lymphoma. Consequently, T-cell lymphomas in CD patients and T-cell lymphomas in the small bowel are always diagnosed as EATLs. However, 25% of EATLs are located extra-intestinal. The most frequent type of T-cell lymphomas is anaplastic large cell lymphoma (ALCL). ALCLs are either anaplastic lymphoma kinase (ALK) negative or positive. EATLs are always ALK negative. As is the case for most EATLs, ALCLs are CD30 positive. CD and EATL are strongly associated with HLA-DQ2 and/or -DQ8. HLADQ2 and/or -DQ8 expression is found in 98% of CD and EATL patients, compared to 40% in the Western population. Aims and Methods: We investigated whether the frequency of HLA-DQ2 and/or -DQ8 is increased in extra-intestinal ALCLs compared to the general population, in order to determine if extra-intestinal ALCLs might in fact be undiagnosed EATLs. For this purpose, extra-intestinal ALCL samples, ALK-positive and ALK-negative, were collected and DNA was isolated. DQA1 and DQB1 alleles were amplified using PCR. HLA-DQ typing was subsequently performed using a single strand conformation polymorphism / heteroduplex based method (SSCP/HD). Results: So far, 21 anaplastic large-cell lymphomas have been HLA-DQ typed. HLA-DQ2 was present in 10 lymphomas, of which 3 were homozygous. HLA-DQ8 was present in 4 lymphomas, all heterozygous. In total, twelve lymphomas (57%) were HLA-DQ2 and/or -DQ8 positive, indicating only a slightly higher prevalence than in the general population. However, within the subgroup of ALKnegative ALCLs, representing potentially undiagnosed EATLs, 71% was HLA-DQ2 and/or DQ8 positive (p=0.05). Conclusion: The increased prevalence of HLA-DQ2 and/or -DQ8 in ALK-negative ALCLs suggests underdiagnosis of EATL within this group of extra-intestinal T-cell lymphomas.