Purpose: To investigate whether celiac disease risk haplotypes HLA-DQ2 and DQ8 also increase the risk for developing small intestinal neuroendocrine tumor (SI-NET).

Methods: Thirty-five patients with serotonin-producing jejunal and ileal SI-NET were examined with HLA-DQ genotyping and serology for IgA anti-tissue transglutaminase (tTG) antibodies.

Results: Twenty-one patients (60 %) carried HLA-DQ2 or DQ8, twice the frequency of the general population (P < 0.001). In particular DQ2 was overrepresented (P = 0.013). Gender, age, disease stage, histopathological grade, or multifocality of primary tumor did not differ between patients with DQ2 or DQ8 and patients with other HLA-DQ haplotypes. No patient in the study was diagnosed with celiac disease (latent or symptomatic) as anti-tTG antibodies were negative in all 35.

Conclusion: HLA-DQ haplotypes associated with celiac disease are overrepresented also in patients with SI-NET, in particular HLA-DQ2.