Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is the inheritance pattern of adrenoleukodystrophy (ALD)?

1. Autosomal dominant

2. Autosomal recessive

3. X-linked dominant

4. X-linked recessive

The correct answer is: X-linked recessive

Adrenoleukodystrophy (ALD) is primarily inherited in an X-linked recessive manner. This means that the gene responsible for ALD is located on the X chromosome. Males, who have only one X chromosome, are at greater risk of being affected by X-linked disorders since they cannot compensate with another X chromosome. In contrast, females have two X chromosomes, and if one carries the mutation, the other X chromosome may mitigate the effects of the disorder, leading to a carrier status or milder manifestations of the disease. In cases of X-linked recessive inheritance, affected males transmit the mutated gene to all of their daughters, who become carriers, but none of their sons. Carrier females have a 50% chance of passing the affected X chromosome to their children, which means there is a 25% chance their sons will be affected and a 25% chance their daughters will also be carriers. This pattern of inheritance is crucial for understanding family dynamics in genetic counseling and risk assessment for offspring of those affected by ALD.