Differential Diagnosis for Elevated GGT with Normal ALT and Bilirubin

Single Most Likely Diagnosis

• Alcoholic Liver Disease: This is often the most common cause of isolated elevated GGT, especially in the context of alcohol consumption. GGT is a sensitive marker for alcohol use and can be elevated even in the absence of significant liver damage, as indicated by normal ALT levels.

Other Likely Diagnoses

• Non-Alcoholic Fatty Liver Disease (NAFLD): Although ALT is often elevated in NAFLD, it can be normal, especially in early stages or in cases where the disease is not actively progressing. GGT can be elevated due to the liver's response to fatty infiltration.
• Drug-Induced Liver Injury: Certain medications can cause an elevation in GGT without significantly affecting ALT or bilirubin levels. The pattern of liver enzyme elevation can vary depending on the offending drug.
• Biliary Tract Disease: Conditions such as chronic biliary obstruction or primary biliary cholangitis can lead to elevated GGT levels. Even if ALT and bilirubin are normal, biliary disease should be considered, especially if there are symptoms suggestive of biliary tract pathology.

Do Not Miss Diagnoses

• Pancreatic Cancer: Although less common, pancreatic cancer can cause elevated GGT, especially if it involves the bile ducts. It's crucial to consider this diagnosis to avoid missing a potentially curable malignancy.
• Primary Sclerosing Cholangitis: This is a chronic liver disease characterized by inflammation and scarring of the bile ducts, which can lead to elevated GGT. Early diagnosis is important for management and potential liver transplantation.

Rare Diagnoses

• Hemochromatosis: A genetic disorder leading to iron overload, which can cause liver damage and elevate GGT. Although ALT might be normal, the disease's progression can lead to significant morbidity if not addressed.
• Wilson's Disease: A rare genetic disorder causing copper accumulation in the liver, which can result in elevated GGT among other liver function abnormalities. Early diagnosis is critical to prevent irreversible liver damage.
• Alpha-1 Antitrypsin Deficiency: A genetic disorder that can cause liver disease and might present with elevated GGT, even if other liver enzymes are normal. It's essential to consider this diagnosis, especially in younger patients or those with a family history of liver disease.