A heterozygous variant causing an amino acid substitution p.(Gly396Asp) in the MutY DNA glycosylase gene (<i>MUTYH</i>) was significantly enriched in SI-NET patients (minor allele frequencies 0.013 and 0.003 for patients and controls respectively) and resulted in odds ratio of 5.09 (95% confidence interval 1.56-14.74; <i>P</i> value = 0.0038).