Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What enzyme do patients with adrenoleukodystrophy (ALD) lack?

1. Enzyme that breaks down short-chain fatty acids

2. Enzyme that breaks down medium-chain fatty acids

3. Enzyme that breaks down very long-chain fatty acids

4. Enzyme that breaks down long-chain fatty acids

The correct answer is: Enzyme that breaks down very long-chain fatty acids

Patients with adrenoleukodystrophy (ALD) lack the enzyme responsible for breaking down very long-chain fatty acids (VLCFAs). This deficiency leads to an accumulation of VLCFAs in the body, particularly in the adrenal glands and nervous system. The buildup of these fatty acids is toxic and contributes to the demyelination of neurons, which is a hallmark of the disease. ALD is linked to mutations in the ABCD1 gene, which encodes the ATP-binding cassette transporter involved in the peroxisomal transport of very long-chain fatty acids. As a result, individuals affected by ALD cannot effectively metabolize VLCFAs, leading to their harmful accumulation and subsequent neurological and adrenal problems. Understanding the specific enzyme deficiency is crucial for diagnosing and managing ALD, as it highlights the metabolic pathway disrupted in affected patients. This knowledge guides therapeutic approaches, including dietary interventions to limit VLCFA intake, and helps in monitoring the disease's progression.