New Terminology for Nonalcoholic Steatohepatitis (NASH)
The term nonalcoholic steatohepatitis (NASH) has been replaced by metabolic dysfunction-associated steatohepatitis (MASH), while nonalcoholic fatty liver disease (NAFLD) has been renamed to metabolic dysfunction-associated steatotic liver disease (MASLD). 1
Background on the Terminology Change
The change in terminology was implemented to address several key issues with the previous nomenclature:
Removal of stigma: The new terminology eliminates the potentially stigmatizing term "fatty" when referring to hepatic steatosis 1
Positive diagnosis approach: Rather than defining the condition by what it is not (non-alcoholic), the new terminology provides a positive diagnosis by identifying the presence of cardiometabolic risk factors associated with insulin resistance 1
Pathophysiological accuracy: The new term better reflects the underlying metabolic dysfunction that drives the development of steatosis 1
Diagnostic Criteria for MASLD/MASH
MASLD is diagnosed in patients with:
- Evidence of hepatic steatosis (≥5% on imaging or histology)
- Presence of at least one cardiometabolic risk factor associated with insulin resistance:
- Prediabetes or diabetes
- Atherogenic dyslipidemia
- Hypertension
- Other metabolic risk factors
- Absence of other identifiable causes of steatosis 1
MASH specifically refers to the more severe form of MASLD characterized by:
- ≥5% hepatic steatosis
- Inflammation and hepatocyte injury (ballooning)
- With or without evidence of liver fibrosis 1
Additional Classification: MetALD
A separate category called metabolic dysfunction and alcoholic liver disease (MetALD) has been created for cases where:
- Alcohol intake exceeds the threshold for MASLD/MASH
- But is less than what would be attributed to alcoholic liver disease 1
Clinical Implications
This terminology change reflects our evolving understanding of the disease as primarily metabolic in nature. The prevalence of MASLD/MASH is particularly high in people with type 2 diabetes, affecting more than 70% of this population 1.
The new terminology helps clinicians focus on the metabolic drivers of the disease and may improve screening practices, which have historically been inconsistent despite the high prevalence of this potentially progressive liver condition in high-risk groups.
Screening Recommendations
For patients with type 2 diabetes or prediabetes, particularly those with obesity or cardiometabolic risk factors, screening for MASLD with clinically significant fibrosis is recommended using the fibrosis-4 index (FIB-4), even with normal liver enzymes 1.