Background and aim: Although an eight-residue insertion in HLA-DQβ1 has been recently identified as a genetic risk factor for idiopathic achalasia, other risk factors are still unknown. In the present study, we carried out an epidemiological survey and a genotype-phenotype (G×P) analysis to gain further insights into the etiology of achalasia.
Methods: We obtained medical data from 696 achalasia patients and 410 controls, as well as their first-degree relatives (2543 of patients and 1497 of controls). For the G×P analysis, we stratified the patients into HLA-DQβ1 insertion carriers and noncarriers.
Results: Our data show that patients are more often affected by viral infections before achalasia onset (P<0.0001, most significantly for varicella zoster virus infections). In addition, allergic (P=0.0005) and autoimmune disorders (P=0.0007, most significantly for psoriasis and Sjögren's syndrome) represent comorbid disease conditions. First-degree relatives of patients also show higher prevalence rates of allergic disorders (P=0.0007) and psoriasis (P=0.016) compared with control relatives. Moreover, the G×P analysis reveals that achalasia is triggered by pregnancies in female HLA-DQβ1 insertion carriers (P=0.031).
Conclusion: Our data point to a role of viral infections in the development of achalasia. In addition, they provide evidence for a relationship between achalasia and allergic, as well as autoimmune, disorders. Furthermore, pregnancy seems to be a disease-triggering factor in female HLA-DQβ1 insertion carriers, which points to hormonal and/or immunosuppressive factors influencing disease development.