Nomenclature Change from NASH/NAFLD to MASH/MASLD

Non-alcoholic steatohepatitis (NASH) and non-alcoholic fatty liver disease (NAFLD) affect a high percentage of the global population, yet the terminology creates stigma and fails to encompass the main driver of liver injury—metabolic syndrome. After many years of debates, experts in the field have come up with new, more appropriate names for these conditions and introduced new terminology for patients who have both metabolic problems and consume alcohol.

A change in nomenclature: NASH becomes MASH

The term non-alcoholic steatohepatitis (NASH) will officially be replaced by metabolic dysfunction-associated steatohepatitis (MASH), while nonalcoholic fatty liver disease (NAFLD) will now be called metabolic dysfunction-associated steatotic liver disease (MASLD).

Instead of NASH/NAFLD, which can be stigmatizing and inaccurate, a new name has been proposed: MASH/MASLD. This name reflects the main cause of liver damage and is intended to help more people receive the proper care and support.

Outside of this, a new category, metabolic and alcohol-associated liver disease (MetALD), has been introduced for people with metabolic syndrome who drink greater amounts of alcohol per week (140 g/week and 210 g/week for females and males, respectively). The occurrence of multiple risk factors in one patient is fairly common.

Steatotic liver disease (SLD) will encompass various causes of liver damage. At the same time, cryptogenic SLD will be used to diagnose patients who have no metabolic or other known causes of liver damage.

The changes in terminology were announced at EASL Congress 2023 by the multinational liver societies leaders from La Asociación Latinoamericana para el Estudio del Hígado (ALEH), American Association for the Study of Liver Diseases (AASLD), and European Association for the Study of the Liver (EASL) as well as the co-chairs of the NAFLD Nomenclature Initiative.

Supporting the new definitions and terminology, a recent study showed that MAFLD affects more than a third of the global population, and most of these patients are overweight or obese adults. The estimated global MAFLD prevalence is from 25% in the general population to 50–60% in obese and diabetic patients. Both patients and the medical community need to use the right nomenclature for such a prevalent condition.

Why is the NASH/NAFLD terminology changing?

Like many other patients, you or someone you know might have felt stigmatized or judged by the term “fatty liver disease.” For a long time, experts were worried this could prevent people from seeking healthcare and tried to develop adequate nomenclature. However, there were significant knowledge gaps in understanding the disease, and it was difficult to agree on the terminology that would properly capture the essence of the condition.

The previous names had several issues: NAFLD and NASH would only mark the presence of fat inside the liver and exclude excessive alcohol use but not explain the actual cause. If you consume alcohol but have metabolic problems causing liver damage, you would only be diagnosed with alcoholic-related liver disease. Similarly, the term did not include patients with chronic, long-lasting liver conditions associated with metabolic issues that contribute to liver injury.

What is MASLD/MASH?

According to recent research findings, the condition previously known as NAFLD is caused by various metabolic factors: being very overweight or obese, especially around the waistline (visceral obesity), having a poor response to insulin and problems with blood sugar regulation, and increased levels of blood fats such (dyslipidemia). These metabolic disorders all contribute to liver injury in different ways and might sometimes appear together. Liver injury can lead to scarring of the liver tissue. If these disorders are not addressed, the scarring may get worse and can lead to more serious conditions, such as cirrhosis and liver failure.

What does this mean for you?

NAFLD and NASH, as terms, encouraged stigma and potentially underestimated the metabolic syndrome causing liver damage. MASLD and MASH may better encompass the different causes of your liver disease. They include metabolic problems or a combination of metabolic problems and alcohol use. These terms also include chronic liver diseases and metabolic factors.

This nomenclature change will enable your provider to perform broader testing and a fair examination of the relative contributions of each factor and their potential joint effects in individuals who have several factors for liver injury. With the right terminology, you should have solid grounds to receive the appropriate health benefits and insurance coverage.

Moreover, the changes have already positively affected the guidelines for medical practice. This will allow physicians and other health providers to more effectively screen at-risk population groups, diagnose the condition more easily, and opt for the right treatment.