['The etiology of achalasia is still unknown. The aim of the present study was to elucidate its underlying pathologies and their chronology by investigation of esophageal specimens in patients undergoing surgery (esophageal resection or myotomy) for achalasia.', 'In 17 patients with achalasia, histopathologic examinations of the esophageal wall focussing on the myenteric plexus were performed. Preoperative diagnosis was based on clinical evaluation, esophagogastroscopy, barium esophagogram in all, and esophageal manometry in eight patients. The median age at the time of surgery was 54 years (range: 14-78 years). In eight cases, the complete esophageal, body and in nine cases a smooth muscle biopsy including parts of the myenteric plexus from the distal part of the esophagus (high pressure zone) was available. The tissue specimens were fixed in formalin and embedded in paraffin. The staining procedures were hematoxylin and eosin (HE), Elastica van Gieson (EvG), and periodic acid-Schiff (PAS) reaction. Immunohistochemical examinations were performed with antibodies against B and T lymphocytes, neurofilament, protein gene-related product (PGP 9.5), S-100 protein, myosin, desmin, smooth muscle actin and substance P.', "In 13 of 17 patients, a significant reduction of the number of intramural ganglion cells was present. Common findings were a severe fibrosis of the smooth muscle layer (10/17) and obvious myopathic changes of the smooth muscle cells (5/17). Staining for B and T lymphocytes found signs of inflammation in mucosal and muscular areas. Three patients exhibited a marked invasion of eosinophilic granulocytes of the muscularis propria (eosinophilia). Esophageal carcinoma had developed in three patients (squamous cell carcinoma in two and carcinoma in situ in another patient with Barrett's esophagus and high-grade dysplasia). Severe inflammatory reactions (neural, eosinophilic and mucosal) dominated in patients with a longstanding history of achalasia (>10 years) as well as a marked endomysial fibrosis."] Does spectrum of histopathologic findings in patients with achalasia reflect different etiologies?