There is accumulating evidence suggesting that an autoimmune component is involved in esophageal achalasia. An increase in immune cells, cytokines, chemokines, and autoimmune antibodies in serum and infiltration of immune cells in tissues support the view that immune-mediated inflammation is a crucial pathogenesis of inhibitory neuron degeneration in the lower esophageal sphincter. Infection of viruses such as the herpes virus family has been suspected of provoking the autoimmune reaction. Meanwhile, previous reports on immunogenetics have proposed that specific risk alleles on the human leukocyte antigen complex define the susceptible population to achalasia. In this study we reviewed current knowledge regarding the immune-related factors of achalasia, including immunology, viral infection and immunogenetic variations. K E Y W O R D S autoimmune diseases, esophageal achalasia, histocompatibility antigens class II, immunology, viruses 1 | INTRODUCTION Esophageal achalasia is a motility disorder that presents with symptoms including dysphagia, regurgitation, chest pain, and weight loss. It is clinically subclassified into three types based on different manifestations in high-resolution manometry: type I achalasia is the classical achalasia with no pressurization; in type II achalasia there is compression of over 30 mmHg in the distal esophagus; while type III achalasia can be diagnosed when two or more spastic contractions are observed. 1 The pathophysiology of this disease is a loss of peristalsis and inadequate relaxation of the lower esophageal sphincter (LES), which results from gradual disappearance of the myenteric neurons. Previous histological studies have found the loss of inhibitory enteric neurons in the esophageal tissues of patients with achalasia. 2 In the nervous system, these types of neurons contain nitric oxide and vasoactive intestinal polypeptide, which are responsible for this process. 7 Achalasia was recognized as a degenerative disease of the myenteric plexus. 8 About three decades ago studies on achalasia revealed inflammatory cell infiltration in the myenteric ganglia. 9 Later reports have demonstrated that the pathogenesis of achalasia is associated with immunology, viral infection, and host genetics. It turns out that immunology is potentially the crucial factor, and viral infection may trigger the disordered immune reaction in specific patients with an immunogenetic variation. In this review, we focused on all the *These three authors contributed equally to this work.