Idiopathic achalasia is a severe motility disorder of the esophagus and is characterized by a failure of the lower esophageal sphincter to relax due to a loss of neurons in the myenteric plexus. Most recently, we identified an eight-amino-acid insertion in the cytoplasmic tail of HLA-DQβ1 as strong achalasia risk factor in a sample set from Central Europe, Italy and Spain. Here, we tested whether the HLA-DQβ1 insertion also confers achalasia risk in the Polish and Swedish population. We could replicate the initial findings and the insertion shows strong achalasia association in both samples (Poland P=1.84 × 10-04, Sweden P=7.44 × 10-05). Combining all five European data sets – Central Europe, Italy, Spain, Poland and Sweden – the insertion is achalasia associated with Pcombined=1.67 × 10-35. In addition, we observe that the frequency of the insertion shows a geospatial north–south gradient. The insertion is less common in northern (around 6–7% in patients and 2% in controls from Sweden and Poland) compared with southern Europeans (~16% in patients and 8% in controls from Italy) and shows a stronger attributable risk in the southern European population. Our study provides evidence that the prevalence of achalasia may differ between populations.European Journal of Human Genetics advance online publication, 6 January 2016; doi:10.1038/ejhg.2015.262.
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