Metabolic dysfunction-associated steatohepatitis (MASH), formally known as nonalcoholic steatohepatitis (NASH), is a liver disease that develops when accumulated liver fat causes inflammation and cellular damage. It’s a severe stage of what was once called nonalcoholic fatty liver disease (NAFLD), now known as metabolic dysfunction-associated steatotic liver disease (MASLD).
When it first develops, MASH often has no symptoms or may only cause general fatigue or discomfort in the abdomen. If the condition progresses, however, its symptoms — such as itching, swelling, excessive bruising, and muscle wasting — will accumulate and become more serious.
Often linked to conditions associated with high blood lipid (fat) levels such as type 2 diabetes and obesity, MASH can lead to lasting liver damage and dangerous conditions such as cirrhosis, liver cancer, and heart issues.
Early on, MASH often is asymptomatic. Many people don’t realize anything is wrong until their liver shows signs of damage from MASH, which can take years to occur.
When they do occur, early MASH symptoms may include:
Persistent fatigue, or feeling tired consistently
Discomfort or pain in the upper right abdomen where your liver sits
Unexplained weight loss
Weakness or general malaise
As cirrhosis damages the liver later in the disease, MASH can have other symptoms, including:
Pruritus, or intense itching
Ascites, or swelling in the abdomen from fluid buildup
Edema, a swelling in the legs
Jaundice, a yellowing of the skin and eyes
Bruising and bleeding easily
Spider angiomas, or blood vessels just under the surface of your skin that look like a spiderweb
Hepatic encephalopathy, or a buildup of blood toxins that can cause behavior changes, slurred speech, and confusion
Red palms
Shortness of breath
Internal bleeding
Muscle wasting
Portal hypertension, or increased pressure in the portal vein that causes the liver and spleen to enlarge
MASH doesn’t appear overnight. It evolves over time as part of MASLD, which is defined by a buildup of unhealthy fat within your liver. The stage of MASH you have depends on how much liver scarring, or fibrosis, you have.
Stage 0 fibrosis is when you have too much fat in your liver but have not yet experienced any liver damage or fibrosis. At this stage, you may be diagnosed with MASLD that hasn’t developed into MASH.
The stages of MASH describe increasing levels of liver damage:
Stage 1: MASH with mild fibrosis indicates an early level of liver scarring that can often be reversed with self-care.
Stage 2: In MASH with moderate fibrosis, inflammation and cellular damage have caused some liver scarring that could be reversed. Your liver is still working well.
Stage 3: MASH with advanced fibrosis includes extensive liver scarring. Some of this damage can be reversed. But at this stage, treatment from healthcare professionals is necessary to prevent further, permanent damage and maintain your liver function.
Stage 4: When cirrhosis sets in at this stage, scarring is severe enough to change your liver’s shape. Some of the scarring is permanent, but some damage may still be reversible. Your liver may still function at a reduced capacity, but liver cancer and failure are serious risks.
Stages 0 and 1 may have no symptoms or general ones, such as weakness or fatigue. As liver damage gets closer to cirrhosis in later stages, more serious symptoms such as jaundice and shortness of breath may occur.
MASH is the third most common cause of hepatocellular carcinoma, which accounts for 90 percent of liver cancer cases. It also can lead to liver failure, in which your liver no longer removes toxins, produces bile, and converts nutrients to energy.Both are serious issues: The five-year survival rate for people with hepatocellular carcinoma is 21 percent, and end-stage liver failure often requires a transplant.
Liver inflammation from MASH also can affect the heart, kidneys, and muscles.
Cardiovascular disease is the most common cause of death in people with MASH. In addition to a heart attack or stroke, MASH can contribute to heart issues that include:
Coronary artery disease
Atherosclerosis, a buildup of plaque in the arteries
Changes in heart size and shape
Heart failure
Arrhythmia, or irregular heartbeat
Muscle-related complications of MASH include:
Muscular atrophy, in which your muscles progressively weaken and degenerate
Sarcopenia, a loss of muscle mass and function
Inflammatory myopathies, rare muscle disorders that include skeletal muscle inflammation
Type 2 diabetes also is a complication of MASH, in addition to being a risk factor for it.
Because MASH symptoms can be vague or nonexistent in early stages, it can be difficult to know if you have MASH before it becomes a serious issue.
To help catch the disease before you develop irreversible liver damage, contact your healthcare provider if you experience these symptoms:
Jaundice
Easy bruising
Dark urine
Swelling in the abdomen or legs
Vomiting blood
Dark or black tarry feces
Periods of confusion, mood changes, forgetfulness, or poor judgment
Unexplained skin itching
MASH is a progressive and potentially serious liver condition, but it may not present symptoms until damage is advanced.
Early MASH may include fatigue, pain in the upper right abdomen, weakness, and unexplained weight loss.
The earlier MASH is detected, the more likely you can halt or even reverse the damage to your liver.
Left untreated, MASH can lead to serious complications such as liver failure and liver cancer, cardiovascular disease and other heart issues, and muscular issues.
