Differential Diagnosis for Elevated AST with Normal Alk Phos

Single Most Likely Diagnosis

• Acute Viral Hepatitis: This condition often presents with elevated AST levels due to liver cell injury, while alkaline phosphatase (alk phos) levels may remain normal, especially in the early stages of the disease. The elevation of AST is typically more pronounced than ALT in the initial phases but can reverse as the disease progresses.

Other Likely Diagnoses

• Alcoholic Liver Disease: Alcohol consumption can lead to an elevation in AST levels, often out of proportion to ALT, with a ratio of AST to ALT greater than 2:1. Alk phos may remain normal unless there is associated cholestasis or bone disease.
• Non-Alcoholic Fatty Liver Disease (NAFLD): While NAFLD typically presents with mild elevations in liver enzymes, AST can be elevated, sometimes more so than ALT, especially in the context of steatohepatitis. Alk phos can be normal or slightly elevated.
• Muscle Injury: Significant muscle injury, such as from trauma or intense exercise, can elevate AST levels due to the release of the enzyme from muscle cells. Alk phos, being more specific to liver and bone, would typically remain normal.

Do Not Miss Diagnoses

• Acute Liver Failure: Although less common, acute liver failure from any cause (e.g., drug-induced, ischemic, or autoimmune hepatitis) can present with markedly elevated AST levels and normal or slightly elevated alk phos. Early recognition is critical for potential liver transplantation.
• Budd-Chiari Syndrome: This rare condition, caused by hepatic vein thrombosis, can lead to acute liver dysfunction with elevated AST and relatively normal alk phos, especially in the early stages. It requires prompt diagnosis and treatment to prevent liver failure.

Rare Diagnoses

• Wilson's Disease: A genetic disorder leading to copper accumulation in the liver, which can cause liver injury and elevated AST. Alk phos may be normal or slightly elevated. It's rare but important to consider in young patients with unexplained liver enzyme elevations.
• Alpha-1 Antitrypsin Deficiency: A genetic disorder that can cause liver disease and elevated AST levels. Alk phos may be normal, especially in the absence of significant cholestasis. It's a rare condition but should be considered in patients with a family history or other suggestive findings.