No eosinophilic and lymphocytic infiltration in lower oesophageal sphincter biopsies from achalasia patients.

INTRODUCTION: Achalasia has been proposed as a muscle-predominant variant of eosinophilic or lymphocytic oesophagitis. Peroral endoscopic myotomy (POEM) enables direct biopsy of the oesophageal muscular layer. We assessed eosinophilic and lymphocytic infiltration in the distal oesophageal muscle. METHODS: We retrospectively analysed POEM patients without mucosal eosinophilia who underwent lower oesophageal sphincter biopsies over 42 months. Eosinophils (EOs) were quantified per mm²; lymphocytes and nerve tissue were assessed by CD3 and S-100 staining. Seven patients with proximal oesophageal cancer served as controls. RESULTS: Among 141 patients (52.4% male; mean age 47.5 years), mean EO density was 0.4/mm²; 10.6% had ≥1 EO/mm². CD3 staining was absent or minimal in most, with mild increases in 5.7%. Lymphocyte density correlated with achalasia subtype (p=0.03), but not with EOs or outcomes. Controls showed negligible inflammation. CONCLUSION: Lower oesophageal sphincter biopsies showed no significant eosinophilic or lymphocytic infiltration, arguing against an inflammatory myopathy as the basis of achalasia.