MASH is the New Name for NASH
Yes, MASH (metabolic dysfunction-associated steatohepatitis) is essentially the same condition as NASH (non-alcoholic steatohepatitis)—it's simply a nomenclature update, not a different disease. 1
Understanding the Terminology Change
The medical community officially replaced NASH with MASH in 2023-2024 as part of a broader renaming of the entire disease spectrum. This change reflects a shift toward positive diagnostic criteria (defining what the disease is based on metabolic dysfunction) rather than negative criteria (defining what it isn't—i.e., "non-alcoholic"). 1, 2
The Complete Nomenclature Evolution:
- NAFLD → MASLD (metabolic dysfunction-associated steatotic liver disease)
- NASH → MASH (metabolic dysfunction-associated steatohepatitis)
- Both terms describe the identical pathological entity with the same histological features: hepatocellular ballooning and lobular inflammation 1
Why the Change Matters Clinically
The new terminology emphasizes that this is fundamentally a metabolic disease requiring the presence of at least one cardiometabolic risk factor (obesity, type 2 diabetes, hypertension, dyslipidemia, or metabolic syndrome). 1 This positive framing:
- Reduces stigma associated with "fatty liver" terminology
- Highlights the metabolic underpinnings requiring treatment
- Aligns nomenclature with pathophysiology
- Facilitates clearer communication with patients
Disease Spectrum Under New Names
The MASLD spectrum includes 1:
- Simple steatosis (MASL - metabolic dysfunction-associated steatotic liver)
- MASH (the inflammatory form, previously NASH)
- Fibrosis stages F0-F4
- MASH-related cirrhosis
- MASH-related hepatocellular carcinoma
Practical Clinical Application
When reading older literature or guidelines mentioning NASH, you can directly substitute MASH—they refer to the same histopathological condition. 3 The 2024 EASL-EASD-EASO guidelines explicitly state that MASH is "previously NASH," confirming these are interchangeable terms for the same disease entity. 1
Key Clinical Point:
All existing NASH research, risk stratification tools, and treatment approaches apply directly to MASH. The American Association for the Study of Liver Diseases confirmed that their NAFLD Practice Guidance remains fully applicable when using the new MASLD/MASH terminology. 3
Treatment Implications
The first FDA-approved medication for this condition, resmetirom, received approval in 2024 specifically for "non-cirrhotic MASH with significant fibrosis (stage ≥F2)." 1 This demonstrates that regulatory agencies and clinical practice are actively transitioning to the new nomenclature while maintaining continuity with the underlying disease understanding.