Hepatic encephalopathy is a neuropsychiatric syndrome that occurs in patients with liver disease. This Primer discusses the epidemiology, pathophysiology, diagnosis and treatment of hepatic encephalopathy, and discusses how this disorder affects the quality of life of patients.

Genetic pain loss disorders are a heterogeneous group of diseases that are characterized by reduced pain sensation. This Primer discusses the epidemiology, pathophysiology, diagnosis and treatment of these disorders.

Congenital diaphragmatic hernia is a rare birth defect associated with cardiopulmonary complications and high mortality and morbidity. This Primer describes the epidemiology and mechanisms of congenital diaphragmatic hernia and discusses diagnosis, management and quality of life for patients.

Trachoma, caused by infection with conjunctival strains of Chlamydia trachomatis, is the most common infectious cause of blindness. This Primer summarizes the epidemiology, pathophysiology and diagnosis of trachoma as well as its management, disease control and elimination, and key areas for future research.

Hypothyroidism is a common condition of insufficient thyroid hormone production or metabolism, which can be life-threatening if untreated. This Primer reviews hypothyroidism epidemiology, pathogenesis, diagnosis, screening and prevention programmes, current treatment approaches, and areas for additional research.

Achalasia is a disorder of the oesophageal smooth muscle characterized by impaired lower oesophageal sphincter relaxation and absent or spastic oesophageal body contractions. This Primer reviews the epidemiology, pathophysiology, diagnosis and management of achalasia, as well as patient quality of life and areas for further research.