creation date: 2025-11-20 20:30
tags: Pathologies
Metabolic Dysfunction-Associated Steatotic Liver Disease
Background
Definitions
Metabolic dysfunction-associated steatotic liver disease (MASLD) refers to a range of diseases characterized by hepatic steatosis seen on imaging or histology.
MASLD is a term that replaces non-alcoholic fatty liver disease (NAFLD) to describe liver fat accumulation without significant alcohol intake. The shift in terminology achieves two things:
- Use of “steatotic” instead of “fatty” avoids stigma
- Use of “non-alcoholic” defines the disease by exclusion which has inherent ambiguity and lack of specificity; use of “metabolic dysfunction-associated” also reflects new evidence indicating pathophysiological mechanisms associated to metabolic syndrome
MASLD is highly prevalent, estimated to be 30% of the general population. The incidence has increased over time.
MASLD is one category of a greater umbrella term, steatotic liver disease, which also includes:
- Metabolic dysfunction-associated steatohepatitis (MASH)
- Metabolic dysfunction and alcohol-associated liver disease (MetALD)
- Alcohol-associated liver disease (ALD)
Etiology
A number of factors are associated with the development of MASLD:
- Obesity
- Diabetes
- Dyslipidemia
- Insulin resistance
- Metabolic syndrome
- Cardiovascular risk factors
Pathogenesis
MASLD encompasses a spectrum of histological features that ranges from fat accumulation in hepatocytes without inflammation or fibrosis to hepatic steatosis with necroinflammation with or without fibrosis (MASH). A number of factors have been implicated in the pathogenesis of MASLD but has not been fully elucidated.
Accumulation of lipids
Steatosis is a manifestation of excess toxic lipids in the liver which includes triglycerides, free fatty acids (FFA), ceramides, and free cholesterol. This can occur from:
- Excessive transport of FFA from adipose tissue (as triglycerides)
- Diminished hepatic export of FFA (decreased VLDL from lack of proteins)
- Impaired beta-oxidation of FFA (eg. vitamin B5 deficiency, excessive alcohol consumption, CoA deficiency)
Insulin resistance
Insulin resistance has a key role in hepatic steatosis. Insulin resistance is thought to cause an increase in FFA and triglyceride delivery to the liver. An excess of carbohydrates can also stimulate de novo fatty acid synthesis.
Development of metabolic dysfunction-associated steatotic hepatitis (MASH)
The excess of fatty acids in the liver makes it more vulnerable to injury. Mechanisms such as peroxisomal fatty acid oxidation, reactive oxygen species production, and cytochrome P450 metabolism of fatty acids may cause injury which results in activation of inflammatory cascades.
This results in ballooning and death to hepatocytes.
Clinical Presentation
Signs & Symptoms
Most patients with MASLD are asymptomatic with symptoms not arising until later progressions of liver disease.
Examination often will find no liver-related abnormalities but may present with hepatomegaly.
History & Physical Exam
Initial evaluation which typically occur following incidental findings include:
- Description of symptoms
- Existing medical conditions
- Medication use (associated medications include amiodarone, glucocorticoids, methotrexate, tamoxifen)
- Family history of liver conditions
- Alcohol consumption
Risk factors
Conditions such as:
- Diabetes or pre-diabetes
- Obesity
- Dyslipidemia
Diagnosis
Criteria
The diagnosis of MASLD is made on the basis of imaging demonstrating liver steatosis in the absence of other etiologies (eg. drug-induced) in the presence of at least one metabolic risk factor.
In cases where imaging or laboratory testing is inconclusive, liver biopsy and histology may be indicated. Liver biopsy may also be used if autoimmune disease is suspected.
Work-up
In patients with suspected MASLD, the following studies are done to assess liver function and comorbid conditions:
- ALT and AST (typically 2-5x ULN, AST/ALT <1; can also be normal)
- ALP (2-3x ULN)
- Total bilirubin and serum albumin (typically normal unless cirrhosis)
- PTT/INR
- CBC with platelets
- Fasting blood glucose and A1C
- Lipid panel
Additional tests for alternative causes include:
- Hepatitis B screening (surface antigen, surface antibody, total core antibody)
- Anti-hep C virus antibody
- IgG and antibodies for autoimmune hepatitis
- Iron panel (for hemochromatosis)
- Antimitochondrial antibody for primary biliary cholangitis
- Ceryuloplasmin (in patients <50 with neurocognitive symptoms) for Wilson disease
- Alpha-1 antitrypsin level for AAT deficiency
- Anti-tissue tTG-IgA for celiac disease
Staging of disease
The goal of staging is to determine the severity of fibrosis. Biopsy is sufficient for evaluation for patients who underwent liver biopsy for diagnosis.
A FIB-4 score is completed to determine fibrosis severity. An elevated score qualifies a patient for further fibrosis assessment.
- Vibration-controlled transient elastography: ultrasound-based measurements of liver stiffness (stiffness correlated to degree of fibrosis)
- Acoustic radiation force impulse (ultrasound-based)
- Magnetic resonance elastography
Differential
The differential diagnoses for conditions associated with liver steatosis include:
- Alcohol-associated liver disease (histologically identical, differentiated by history)
- Chronic hepatitis C virus infection
- Wilson disease
- Parenteral nutrition
- Drug-induced liver disease
- Other genetic diseases (typically found in pediatric patients)
Red Flags / Complications
The primary complication of MASLD is progression to symptomatic and more advanced forms of steatotic liver disease.
Management
General Measures
For all patients with MASLD:
- Abstain from alcohol - >14 drinks per week or >4 drinks per day for males / >7 per week or >3 drinks per day for females associated with disease progression. Light-to-moderate alcohol consumption is unclear effect on progression
- Immunizations - Hep A and B vaccine for those without serological immunity; chronic liver disease include pneumococcal and routine immunizations
- Modify risk factors for CVD - may include lipid lowering therapy and blood glucose control
- Coffee consumption - at least two cups daily reduces risk of fibrosis progression
- Vitamin D - supplementation as needed
For patients who are overweight/obese, weight loss is recommended. This includes diet modification and exercise. GLP-1-related drug therapies or bariatric surgery may be indicated for patients unable to meet weight loss goals after six months.
- 0.5-1kg per week to lose 5-7% of body weight
Pharmacological / Interventional
The primary purpose of pharmacological therapy is for treatment of significant fibrosis. This is discussed separately.
Monitoring
Following diagnosis, ALT and AST are obtained every 3-6 months to monitor improvements following lifestyle interventions and weight loss benefits.
Biopsy may also be used for assessment of fibrosis.