Gastroenterology · Metabolic Dysfunction-Associated Steatotic Liver Disease
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Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly nonalcoholic fatty liver disease (NAFLD), is hepatic steatosis plus ≥1 cardiometabolic risk factor; it is strongly associated with metabolic syndrome, specifically obesity, type 2 diabetes mellitus, and hypertriglyceridemia, and its inflammatory form (formerly NASH) is now MASH.
The reference standard for definitive diagnosis and staging of metabolic dysfunction-associated steatohepatitis (MASH) remains a liver biopsy showing steatosis, lobular inflammation, and hepatocyte ballooning degeneration (Mallory-Denk bodies may be present but are not required).
Patients typically present with asymptomatic elevation of ALT and AST with an AST:ALT ratio < 1, distinguishing it from the AST:ALT > 2:1 ratio seen in alcohol-associated liver disease.
First-line management for patients with MASLD is lifestyle modification focusing on weight loss through caloric restriction and physical activity.
Resmetirom (FDA-approved 2024) and semaglutide (FDA-approved 2025) are approved for MASH with F2-F3 fibrosis; pioglitazone or GLP-1 receptor agonists are preferred in patients with biopsy-proven MASH and comorbid type 2 diabetes.
Non-invasive testing begins with FIB-4 (a value ≥1.3 prompts further testing), followed by transient elastography (FibroScan) or ELF, to risk-stratify for advanced fibrosis or cirrhosis.
Patients with MASLD are at increased risk for hepatocellular carcinoma (HCC), even in the absence of established cirrhosis.
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A 52-year-old male with a history of type 2 diabetes and obesity presents for a routine follow-up. Physical examination reveals a BMI of 34 kg/m² and mild hepatomegaly. Laboratory studies show an ALT of 88 U/L and an AST of 52 U/L. A liver ultrasound demonstrates increased echogenicity consistent with hepatic steatosis. The patient denies alcohol use and viral hepatitis serologies are negative.
What is the most appropriate initial management for this patient?
Lifestyle modification with weight loss
The patient presents with classic features of MASLD (hepatic steatosis plus cardiometabolic risk factors such as obesity and type 2 diabetes, without significant alcohol use); first-line treatment across disease severity is lifestyle modification to achieve weight loss, which is proven to improve steatosis, steatohepatitis, and fibrosis.
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Etiology / Epidemiology
Defined by hepatic steatosis plus ≥1 cardiometabolic risk factor (e.g., obesity, type 2 diabetes, hypertension, dyslipidemia); strongly associated with metabolic syndrome. Often termed the hepatic manifestation of insulin resistance.
Clinical Manifestations
Usually asymptomatic; may present with hepatomegaly or RUQ discomfort. Elevated ALT > AST is the classic biochemical pattern.
Diagnosis
Liver biopsy is the reference standard for diagnosing and staging MASH. FIB-4 is the first-line non-invasive risk-stratification test, with FibroScan (transient elastography) or ELF as the second step when FIB-4 is ≥1.3.
Treatment
Weight loss (7-10%) is the primary intervention. Resmetirom and semaglutide are FDA-approved for noncirrhotic MASH with F2–F3 fibrosis; pioglitazone or Vitamin E remain options for biopsy-proven MASH.
Prognosis
Risk of progression to cirrhosis and hepatocellular carcinoma. Monitor for decompensated liver failure.
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Epidemiology & Etiology
MASLD (metabolic dysfunction-associated steatotic liver disease, formerly NAFLD) is the most common cause of chronic liver disease in developed nations. It is driven by insulin resistance leading to increased free fatty acid flux to the liver. Patients typically present with obesity, dyslipidemia, and hypertension.
Pertinent Anatomy
Fat accumulation occurs primarily in the hepatocytes (steatosis). Chronic inflammation leads to perisinusoidal fibrosis, often described as a chicken-wire pattern on histology.
Pathophysiology
Excessive caloric intake overwhelms hepatic lipid metabolism, causing triglyceride accumulation. This triggers oxidative stress and cytokine release, progressing from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), formerly nonalcoholic steatohepatitis. Persistent inflammation activates stellate cells, resulting in fibrosis, which can regress with sustained weight loss or effective pharmacotherapy.
Clinical Manifestations
Most patients are asymptomatic, identified incidentally by elevated transaminases. Physical exam may reveal hepatomegaly or signs of advanced disease like spider angiomata. Red flags include jaundice, ascites, or encephalopathy, indicating progression to cirrhosis.
Diagnosis
Diagnosis of MASLD requires hepatic steatosis on imaging or biopsy plus ≥1 of 5 cardiometabolic criteria (overweight/obesity or increased waist circumference, prediabetes/type 2 diabetes, hypertension, hypertriglyceridemia, or low HDL) and exclusion of other causes (e.g., medications, viral hepatitis). Patients with MASLD who also drink moderate amounts of alcohol (about 140–350 g/week in women, 210–420 g/week in men) are classified as MetALD; heavier intake indicates alcohol-associated liver disease. Liver biopsy remains the reference standard to distinguish simple steatosis from MASH. FibroScan is used to quantify liver stiffness and assess fibrosis stage.
Treatment
The cornerstone of therapy is lifestyle modification focusing on diet and exercise to achieve 7-10% weight loss. Pioglitazone is used in patients with biopsy-proven MASH, though weight gain is a common side effect. Vitamin E (800 IU/day) is an alternative for non-diabetic patients, but prostate cancer risk should be considered.
Prognosis
Patients with MASH are at significant risk for cirrhosis and hepatocellular carcinoma (HCC). Surveillance for HCC via ultrasound every 6 months (with or without AFP) is recommended for patients with cirrhosis; AASLD does not recommend routine HCC surveillance in noncirrhotic patients.
Differential Diagnosis
Alcohol-Associated Liver Disease: AST:ALT ratio > 2:1
Hepatitis C: Positive HCV antibody/RNA
Hemochromatosis: Elevated ferritin and transferrin saturation
Wilson Disease: Low ceruloplasmin and Kayser-Fleischer rings
Autoimmune Hepatitis: Elevated ANA, ASMA, and IgG levels