MASLD: key terms to understand

Disease names change over time. In many cases, new names emerge as our knowledge of a condition increases and improves, a name that better aligns with what is now known. One example is the update of non-alcoholic fatty liver disease (NAFLD) to metabolic dysfunction-associated steatotic liver disease (MASLD).

These updates were done in hopes of reducing stigma surrounding these conditions and to emphasize the underlying contributing factors, which are related to problems with metabolism, such as insulin resistance, elevated blood glucose levels, obesity, and diabetes.

Patient education is an important aspect of managing any health condition, including conditions that affect the liver. Patient education means learning more about the condition, what contributes to it, what medical researchers know and what they are trying to answer, and how the condition can be treated and managed.

With that in mind, below are some key terms and concepts that can be helpful to know when learning more about MASLD.

Steatotic liver disease

Steatosis is a clinical term that describes a buildup of fat molecules inside an organ, and steatotic liver disease is an updated term for fatty liver disease. This is an umbrella term that includes MASLD and other diseases characterized by a buildup of fat inside the liver.

How does fat build up inside the liver?

The liver has hundreds of different functions. Among these functions are processing dietary fats, processing fat that is released by fat tissues in different areas of the body, and producing fats (like cholesterol) that the body needs for cellular repair and other functions. When a person has a form of steatotic liver disease, the liver is not able to fully perform these functions. As a result, excess fats accumulate in the liver.

MASH and NASH

The update to MASLD also changes the name of the more advanced form of this condition from nonalcoholic steatohepatitis (NASH) to metabolic dysfunction-associated steatohepatitis (MASH).

Steatohepatitis is more advanced than steatosis. In addition to excess fat in the liver, with steatohepatitis there is also inflammation, damage to liver tissue, and some amount of scarring (fibrosis).

Another term to know is cirrhosis. This is a term for severe scarring of the liver and can occur in the advanced stages of MASH and other types of steatotic liver disease. With cirrhosis, there is severe scarring. This scarring interferes with the liver’s ability to function and changes the structure of the liver. Cirrhosis is irreversible and can lead to liver failure and liver cancer.

What is inflammation and how does it occur?

Inflammation is the body’s response to injuries, germs, harmful chemicals, and toxins. Like many things in the human body, it’s a complex process, but the basic idea is that the body sends large amounts of immune cells to the part of the body that is damaged or infected.

• Acute inflammation is short term and temporary—it’s the type of inflammation you’ll experience if you have a mild cold or a minor injury.
• Chronic inflammation is abnormal inflammation that occurs over a long period of time, causing repeated damage to cells and tissues. This is the type of inflammation that occurs in the liver with MASH. It leads to scarring in the liver as tissues are repeatedly damaged and attempt to heal.

MetALD and ALD

Another new term is metabolic dysfunction and alcoholic liver disease (MetALD). This is a form of steatotic liver disease where both alcohol use and metabolic dysfunction are contributing factors. The term alcohol-related liver disease (ALD) refers to steatotic liver disease where alcohol use is the primary contributing factor.

Your best source of information

If you or a loved one is living with any form of liver disease, your best source of information about the diagnosis and treatment options will be a healthcare provider. Treatment will depend on the type of liver disease a person has, but often focuses on changes to diet and lifestyle, managing risk factors, and treating coexisting conditions.

In addition to updating how we understand and talk about different forms of liver disease, medical research also continues to improve how these conditions are treated. A new drug that can be used to treat MASH with fibrosis (but without cirrhosis) became available in 2024.