Macro-AST: misleading finding in an adolescent with MCAD-deficiency

Area of Science:

• Biochemistry
• Metabolic Disorders
• Clinical Diagnostics

Background:

• Medium-chain acyl-CoA dehydrogenase deficiency (MCAD) is a common inherited metabolic disorder of fatty acid oxidation, often detected through newborn screening.
• Patients with MCAD deficiency can experience metabolic decompensation during catabolic states, leading to organ dysfunction.

Observation:

• A case of an 11-year-old female with MCAD deficiency presented with isolated elevated aspartate aminotransferase (AST) levels.
• No clinical or biochemical signs of organ dysfunction were present in the patient.
• Polyethylene glycol precipitation confirmed macro-AST formation as the cause of the elevated AST, likely due to AST complexing with immunoglobulins.

Findings:

• Macro-AST formation is a non-specific biochemical finding that can occur in individuals with or without MCAD deficiency.
• The isolated AST elevation in this MCAD patient was coincidental and not indicative of disease-specific organ damage.
• Initial diagnostic workup, including ultrasound, ECG, and echocardiography, revealed no abnormalities.

Implications:

• Considering macro-AST formation is crucial when interpreting isolated AST elevations to avoid unnecessary, costly, and invasive diagnostic procedures.
• This diagnostic consideration applies to both healthy individuals and patients with chronic conditions like MCAD deficiency.
• Accurate interpretation of biochemical markers prevents misdiagnosis and ensures appropriate patient management.