Primary sclerosing cholangitis (PSC) is a chronic progressive inflammation and fibrosis of the intrahepatic and extrahepatic bile tracts. This Primer presents the available knowledge on PSC as well as the numerous challenges and unmet needs while shedding light into the ‘black box of hepatology’.

In this Primer, Loomba and colleagues discuss the epidemiology, current understanding of pathophysiology, diagnosis and management of metabolic dysfunction-associated steatotic liver disease, the most common chronic liver disease worldwide, affecting 30% of the adult population.

Bullous pemphigoid is an autoimmune skin disease characterized by tense blisters and erosions. In this Primer, Akbarialiabad et al. review the epidemiology, pathophysiology, diagnosis and management of this disease, and highlight the quality of life of patients and future research areas.

Osteoarthritis is a complex, multifactorial disorder affecting the entire joint that can cause pain and is a leading cause of disability and premature work loss. In this Primer, Tang and colleagues summarize the epidemiology, pathophysiology, diagnosis and management of osteoarthritis and highlight the global burden of the disease.

Chronic kidney disease is the progressive and irreversible loss of kidney function. In this Primer, Romagnani et al. describe the epidemiology and pathophysiology of this disease, and summarize its diagnosis and management, explaining how understanding and treating all modifiable risk factors can slow the progression of chronic kidney disease and prevent or attenuate its consequences.

Cushing syndrome (CS) is defined by signs and symptoms caused by hypercortisolism. In this Primer, Nieman and colleagues outline the causes of endogenous CS and discuss epidemiology, pathophysiology, diagnosis and management of different aetiologies of endogenous CS.