What are the stages of MASLD and MASH?

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a condition that occurs when excess fat accumulates in the liver. MASLD was previously known as nonalcoholic fatty liver disease (NAFLD). As its former name implies, it is not associated with excess alcohol consumption (though other types of liver disease are).

MASLD is estimated to affect over 30 percent of adults worldwide. It’s associated with metabolic disorders that affect how the body processes and stores fat, including obesity, type 2 diabetes, and other metabolic disorders.

MASLD stages and progression

MASLD is a progressive condition, meaning it can get worse over time. Early treatment can help slow progression and prevent complications. Here is an overview of the stages of MASLD:

Stage 0 to stage 1: Simple steatosis

Steatosis is a clinical term for "fatty liver." At this stage, there is fat accumulation in the liver, but the liver is otherwise healthy. Tests will show no signs of enlargement, inflammation, or liver damage. There are usually no symptoms, but a healthcare provider may order tests and exams to check the health of the liver because of other health conditions (such as diabetes or metabolic disorder).

Stage 2: MASH

This stage is called metabolic dysfunction-associated steatohepatitis (MASH), formerly known as nonalcoholic steatohepatitis (NASH). Steatohepatitis is fat accumulation accompanied by inflammation and some damage to the liver. Many people do not experience symptoms at this stage, but some will experience fatigue, discomfort in the upper right abdomen, and a general sense of feeling unwell.

Stage 3: MASH with fibrosis

As inflammation and damage worsen and continue, fibrosis can occur. Fibrosis is the replacement of healthy tissue with scar tissue. While it is a complex biological process, the basic idea is that inflammation damages healthy liver cells and scar tissue forms as the liver heals. When this process occurs over a long period of time, there is less healthy liver tissue and more scar tissue.

Stage 4: MASH with cirrhosis

Cirrhosis is advanced, widespread scarring in the liver. At this stage, significant fibrosis has occurred, enough to change the structure of the liver and impair the normal functioning of the liver. Symptoms of cirrhosis can include jaundice (yellowing of skin and eyes), fluid accumulation in the abdomen, leg swelling, easy bruising, itchiness, and mental confusion. However, many people do not experience symptoms. Cirrhosis increases the risk of liver cancer and liver failure, and it may require liver transplantation.

Having multiple risk factors will put a person at a greater risk for disease progression. Reducing and controlling risk factors is an important part of treatment at all stages.

Treating MASLD and preventing progression

Because MASLD and MASH can progress without causing symptoms, it is important to talk to a healthcare provider about the health of your liver, especially if you have risk factors for these conditions. Risk factors include:

• Having insulin resistance or type 2 diabetes
• Having overweight/obesity, especially with excess abdominal fat
• Having hypertension (high blood pressure)
• Having elevated triglycerides and cholesterol levels
• Having a close family member with MASLD

Reducing weight and addressing coexisting conditions and risk factors can help slow the progression of this disease and are the main focus of treatment. Changes to diet and exercise habits are an essential part of treatment and support multiple treatment goals. A person may also be prescribed different medications to help meet these treatment goals.

A medication to treat MASH with moderate-to-advanced fibrosis (but without cirrhosis) became available in 2024. This medication helps reduce fat accumulation in the liver and has been shown to reduce fibrosis in some instances. This medication should be used along with diet and exercise.

Another important part of treatment is regular appointments to monitor the health of the liver, check for signs of disease progression, and make adjustments to a treatment plan. A healthcare provider will be your best source of information.