Cytokines and the pathogenesis of non-alcoholic steatohepatitis.

Correspondence to: Professor A M Diehl, Duke University Medical Center, Box 3256, Snyderman/GSRB-1, 595 LaSalle St, Durham, NC 27710, USA; diehl004@ mc.duke.edu _________________________ ‘‘PRIMARY’’ NASH AND THE DYSMETABOLIC SYNDROME Histopathological characteristics distinguish steatohepatitis from other causes of chronic liver injury. For years, the main cause of steatohepatitis was thought to be excessive consumption of alcohol. Increasingly, steatohepatitis is being diagnosed in individuals who deny alcohol abuse. Arbitrarily, ‘‘non-alcoholic’’ steatohepatitis (NASH) is subcategorised into ‘‘primary’’ and ‘‘secondary’’ NASH. Primary NASH refers to steatohepatitis that is associated with the dysmetabolic syndrome (that is, obesity, type 2 diabetes, dyslipidaemia). Primary NASH is thought to be the predominant form of NASH, afflicting at least as many individuals in the USA as chronic hepatitis C. Secondary NASH refers to steatohepatitis that accompanies other syndromes (for example, lipodystrophy) or that is caused by certain drugs (for example, amiodarone). Accumulating evidence suggests that common mechanisms may mediate the pathogenesis of alcohol induced steatohepatitis and primary NASH. Although unproven, it is likely that primary and secondary NASH also share common pathogenic mechanisms.